feat: github actions extension linter-ignore file and ignore settings

**Is your feature request related to a problem? Please describe.**

In certain GitHub actions, deprecated fields or configurations that are caught by the GitHub actions VSCode extension's linter do still work or exist in certain versions of a GitHub action.

For example, in the screenshot below, the `command: manifest` configuration in Google's release-please GitHub action does still function, but GitHub actions VSCode extension still considers this an error.


**Describe the solution you'd like**

I want to be able to add a new comment OR surrounding comments OR a VSCode extension settings file (local to workspace, directory, or user) that will suppress the GitHub actions VSCode extension's linter from highlighting an error.

E.g., adding `// gh-actions-ignore` to a line suppresses the linter, OR adding a `.githubactionsignore` file will allow certain files to go unread by the extension (similar to `.gitignore`), OR a general regex filter in the extensions' VSCode settings

**Additional context**

N/A

No source file or test is named. Start by tracing how the GitHub Actions VS Code extension linter reports errors and how workspace, directory, or user settings are handled. Done means users can suppress selected linter errors through a documented mechanism, with coverage for the chosen ignore behavior.

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