CodeQL: ignore some folders

[ibc]

Must tell .github/workflows/codeql.yml to ignore these folders:

art
doc
rust/benches
rust/examples
rust/examples-frontend
worker/deps
worker/subprojects
worker/scripts
worker/fuzzer
worker/out

There is a paths-ignore field in CodeQL that is just valid for interpreted languages (Python, JS, TS), however it doesn't work for compiled languages in which complex stuff must be done.

I found this but I don't understand it plus it seems to be outdated for CodeQL v1 CI actions.

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UPDATE: As discussed here https://github.com/orgs/community/discussions/42654, .gitattributes is no longer valid to tell Code Search which folders to include/exclude, so:

This is not currently possible. If you're in the new Code Search beta you can exclude paths from your search by using a regex like this: NOT path:/worker\/deps/

For now I'll remove .gitattributes from mediasoup repo since it has zero value now.

[ibc]

As discussed here https://github.com/orgs/community/discussions/42654, .gitattributes is no longer valid to tell Code Search which folders to include/exclude, so:

This is not currently possible. If you're in the new Code Search beta you can exclude paths from your search by using a regex like this: NOT path:/worker\/deps/

For now I'll remove .gitattributes from mediasoup repo since it has zero value now.