Add JSON deposit data to create

Cargo.lock

@@ -20,6 +20,8 @@ dependencies = [
  "filesystem",
  "safe_arith",
  "sensitive_url",
+ "serde",
+ "serde_json",
  "slashing_protection",
  "slot_clock",
  "tempfile",
@@ -7342,10 +7344,12 @@ dependencies = [
  "deposit_contract",
  "derivative",
  "eth2_keystore",
+ "eth2_serde_utils",
  "filesystem",
  "hex",
  "lockfile",
  "rand 0.8.5",
+ "serde",
  "tempfile",
  "tree_hash",
  "types",