Update docs for v0.3.0 (#1742)

## Issue Addressed

NA

## Proposed Changes

- Remove Metamask deposits from the docs.
    - Restructure docs to be launchpad-centric.
- Remove references to sigp/lighthouse-docker.
- Add section about binaries.


## Additional Info

Please provide any additional information. For example, future considerations
or information useful for reviewers.

book/src/testnet-validator.md

@@ -0,0 +1,162 @@
+# Become a Testnet Validator
+
+Joining an Eth2 testnet is a great way to get familiar with staking in Phase 0.
+All users should experiment with a testnet prior to staking mainnet ETH.
+
+## Supported Testnets
+
+Lighthouse supports four testnets:
+
+- [Medalla](https://github.com/goerli/medalla/tree/master/medalla) (default)
+- [Zinken](https://github.com/goerli/medalla/tree/master/zinken)
+- [Spadina](https://github.com/goerli/medalla/tree/master/spadina) (deprecated)
+- [Altona](https://github.com/goerli/medalla/tree/master/altona) (deprecated)
+
+When using Lighthouse, the `--testnet` flag selects a testnet. E.g.,
+
+- `lighthouse` (no flag): Medalla.
+- `lighthouse --testnet medalla`: Medalla.
+- `lighthouse --testnet zinken`: Zinken.
+
+Using the correct `--testnet` flag is very important; using the wrong flag can
+result in penalties, slashings or lost deposits. As a rule of thumb, always
+provide a `--testnet` flag instead of relying on the default.
+
+> Note: In these documents we use `--testnet MY_TESTNET` for demonstration. You
+> must replace `MY_TESTNET` with a valid testnet name.
+
+## Joining a Testnet
+
+There are five primary steps to become a testnet validator:
+
+1. Create validator keys and submit deposits.
+1. Start an Eth1 client.
+1. Install Lighthouse.
+1. Import the validator keys into Lighthouse.
+1. Start Lighthouse.
+1. Leave Lighthouse running.
+
+Each of these primary steps has several intermediate steps, so we recommend
+setting aside one or two hours for this process.
+
+### Step 1. Create validator keys
+
+The Ethereum Foundation provides an "Eth2 launch pad" for each active testnet:
+
+- [Medalla launchpad](https://medalla.launchpad.ethereum.org/)
+- [Zinken launchpad](https://zinken.launchpad.ethereum.org/)
+
+Please follow the steps on the appropriate launch pad site to generate
+validator keys and submit deposits. Make sure you select "Lighthouse" as your
+client.
+
+Move to the next step once you have completed the steps on the launch pad,
+including generating keys via the Python CLI and submitting gETH/ETH deposits.
+
+### Step 2. Start an Eth1 client
+
+Since Eth2 relies upon the Eth1 chain for validator on-boarding, all Eth2 validators must have a connection to an Eth1 node.
+
+We provide instructions for using Geth (the Eth1 client that, by chance, we ended up testing with), but you could use any client that implements the JSON RPC via HTTP. A fast-synced node should be sufficient.
+
+#### Installing Geth
+
+If you're using a Mac, follow the instructions [listed here](https://github.com/ethereum/go-ethereum/wiki/Installation-Instructions-for-Mac) to install geth. Otherwise [see here](https://github.com/ethereum/go-ethereum/wiki/Installing-Geth).
+
+#### Starting Geth
+
+Once you have geth installed, use this command to start your Eth1 node:
+
+```bash
+ geth --goerli --http
+```
+
+### Step 3. Install Lighthouse
+
+*Note: Lighthouse only supports Windows via WSL.*
+
+Follow the [Lighthouse Installation Instructions](./installation.md) to install
+Lighthouse from one of the available options.
+
+Proceed to the next step once you've successfully installed Lighthouse and view
+its `--version` info.
+
+> Note: Some of the instructions vary when using Docker, ensure you follow the
+> appropriate sections later in this guide.
+
+### Step 4. Import validator keys to Lighthouse
+
+When Lighthouse is installed, follow the [Importing from the Ethereum 2.0 Launch
+pad](./validator-import-launchpad.md) instructions so the validator client can
+perform your validator duties.
+
+Proceed to the next step once you've successfully imported all validators.
+
+### Step 5. Start Lighthouse
+
+For staking, one needs to run two Lighthouse processes:
+
+- `lighthouse bn`: the "beacon node" which connects to the P2P network and
+	verifies blocks.
+- `lighthouse vc`: the "validator client" which manages validators, using data
+	obtained from the beacon node via a HTTP API.
+
+Starting these processes is different for binary and docker users:
+
+#### Binary users
+
+Those using the pre- or custom-built binaries can start the two processes with:
+
+```bash
+lighthouse --testnet MY_TESTNET bn --staking
+```
+
+```bash
+lighthouse --testnet MY_TESTNET vc
+```
+
+#### Docker users
+
+Those using Docker images can start the processes with:
+
+```bash
+$ docker run \
+	--network host \
+	-v $HOME/.lighthouse:/root/.lighthouse sigp/lighthouse \
+	lighthouse --testnet MY_TESTNET bn --staking --http-address 0.0.0.0
+```
+
+```bash
+$ docker run \
+	--network host \
+	-v $HOME/.lighthouse:/root/.lighthouse \
+	sigp/lighthouse \
+	lighthouse --testnet MY_TESTNET vc
+```
+
+### Step 6. Leave Lighthouse running
+
+Leave your beacon node and validator client running and you'll see logs as the
+beacon node stays synced with the network while the validator client produces
+blocks and attestations.
+
+It will take 4-8+ hours for the beacon chain to process and activate your
+validator, however you'll know you're active when the validator client starts
+successfully publishing attestations each epoch:
+
+```
+Dec 03 08:49:40.053 INFO Successfully published attestation      slot: 98, committee_index: 0, head_block: 0xa208…7fd5,
+```
+
+Although you'll produce an attestation each epoch, it's less common to produce a
+block. Watch for the block production logs too:
+
+```
+Dec 03 08:49:36.225 INFO Successfully published block            slot: 98, attestations: 2, deposits: 0, service: block
+```
+
+If you see any `ERRO` (error) logs, please reach out on
+[Discord](https://discord.gg/cyAszAh) or [create an
+issue](https://github.com/sigp/lighthouse/issues/new).
+
+Happy staking!