Add gamedata/spells endpoint

[VeryGreatFrog]

This should have existed.
https://avrae.readthedocs.io/en/stable/automation_ref.html#CastSpell.id

Summary

Add the endpoint for spells gamedata that should have existed according to the documentation. There is no other way to get this data, as gamedata/entitlements is incomplete when it comes to SRD spells.

Checklist

PR Type

• This PR is a code change that implements a feature request.
• This PR fixes an issue.
• This PR adds a new feature that is not an open feature request.
• This PR is not a code change (e.g. documentation, README, ...)

Other

• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• If code changes were made then they have been tested.
• I have updated the documentation to reflect the changes.

[VeryGreatFrog]

Having finally been able to test it, this endpoint actually shows more data than I was expecting. Hold on tight for some changes

[VeryGreatFrog]

Tested and works as expected.

ready to merge @SeanStoves

[VeryGreatFrog]

Alternatively, it can also be changed to show similar to how entitlements show their data, with their type, link to beyond, entity type, etc, but I don't think that is terribly useful.

[SeanStoves]

@VeryGreatFrog , if you can run blackify on it, I'll get it merged ;)

[VeryGreatFrog]

@SeanStoves I gotta be honest, I don't have that set up well and it is failing not on my code, so not something I am going to concern myself with!