Add SSZ examples

[nflaig]

• add ssz examples in addition to json
• add SignedValidatorRegistrationV1 example
• fix lint warnings due to example/schema mismatches
• update examples that contained invalid data

Note: I did not reference the ssz examples in the schema itself as swagger doesn't display them correctly, which is a known issue.

[nflaig]

bumping beacon-api was required to get rid of lint warnings as some schemas were fixed upstream

[bharath-123]

thanks for this! it would be really nice to have a test script which validates the ssz. Should be easy since we know the types?

[nflaig]

it would be really nice to have a test script which validates the ssz. Should be easy since we know the types?

It would require to bring in a full ssz library into this repo as the spec right now is not executable. Maybe a script to generate ssz examples from json could be useful but there aren't that many examples so I just manually did it using https://simpleserialize.com/.

[bharath-123]

For now, reviewers will have to manually verify whether the ssz and json match. Going forward we could figure out a CI action to verify this.