add automated release workflow (#2077)

## Issue Addressed

Resolves #1674 

## Proposed Changes

- Whenever a tag is pushed with the prefix `v` this workflow is triggered
- creates portable and non-portable binaries for linux x86_64, linux aarch64, macOS
  - an attempt at using github actions caching
- signs each binary using GPG
- auto-generates full changelog based on commit messages since the last release
- creates a **draft** release
- hot new formatting (preview [here](https://github.com/realbigsean/lighthouse/releases/tag/v0.9.23))
- has been taking around 35 minutes

## Additional Info

TODOs:
- Figure out how we should automate dockerhub's version tag. 
  - It'd be quickest just to tag `latest`, but we'd need to make sure the docker workflow completes before this starts
- we do the same cross-compile in the `docker` workflow, we could try to use the same binary
- integrate a similar flow for unstable binaries (`-rc` tag?)
- improve caching, potentially use sccache
- if we start using a self-hosted runner this'll require some re-working

Need to add the following secrets to Github: 

- `GPG_PASSPHRASE`
- ~~`GPG_PUBLIC_KEY`~~ hard-coded this, because it was tough manage as a secret
- `GPG_SIGNING_KEY` 


Co-authored-by: realbigsean <seananderson33@gmail.com>

.github/workflows/docker.yml

@@ -22,6 +22,7 @@ jobs:
             BRANCH_NAME: ${{ steps.extract_branch.outputs.BRANCH_NAME }}
     build-docker-arm64:
         runs-on: ubuntu-18.04
+        environment: protected
         needs: [extract-branch-name]
         # We need to enable experimental docker features in order to use `docker buildx`
         env:
@@ -60,6 +61,7 @@ jobs:
                       --push
     build-docker-amd64:
         runs-on: ubuntu-18.04
+        environment: protected
         needs: [extract-branch-name]
         steps:
             - uses: actions/checkout@v2