Add slang-server configuration schema

[jeet-dekivadia]

Summary

• add a SchemaStore catalog entry for slang-server's .slang/server.json and .slang/local/server.json files
• add a draft-07 version of the generated slang-server configuration schema for broad editor compatibility
• cover the schema with positive and negative validation fixtures

Addresses hudson-trading/slang-server#360.

Validation

• git diff --check
• jq empty src/api/json/catalog.json src/schemas/json/slang-server.json src/test/slang-server/server.json src/negative_test/slang-server/invalid-doc-comment-format.json
• Full SchemaStore validation deferred to CI

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.

[evanwporter]

Hi Jeet, thanks for taking the time to create this PR. When I raised the relevant issue (hudson-trading/slang-server#360), it was intended for @AndrewNolte to make this PR since he's the maintainer and the one who should probably be in the code owner file. Sorry for the confusion.

[jeet-dekivadia]

Thanks for clarifying, and apologies for the mix-up. I am closing this so @AndrewNolte can submit the code-owner change in the intended form.