docs: add linting and code snippet validation

[sarahxsanders]

Description

This PR introduces linting and code snippet validation for GraphQL snippets. JS snippets are commented out on this PR, because I will modernize the JS code snippets first.

Changes

• Updated ESLint config to lint Markdown and MDX files in the repository + special handling for documentation snippets.
• Created a validate-snippets.js script that extracts code snippets from MDX files and validates them against parsers. Note, I temporarily commented out JS validation logic until those code snippets are modernized to meet the latest standards.
• Set up docs validation workflow for GHA to run on PRs. This checks for broken links and code snippets.
• Fix: Added <!-- snippet-ignore --> for GQL snippets causing errors

Comments

• If this looks good, I will expand the same logic/implementation to https://github.com/graphql/graphql-js

Review

• @benjie

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• ✅ login: sarahxsanders / name: Sarah Sanders (9bd1543, 5a8dad1, 195e440, 60e1830, e6b5b29, 4fe6cee)
• ✅ login: saihaj / name: Saihajpreet Singh (a829d13, c469154)

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Name	Status	Preview	Comments	Updated (UTC)
graphql-github-io	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 24, 2025 9:03am

[benjie]

This is awesome! I'm going to integrate some of the improvements here into my own software! 😁

I've left some small suggested tweaks below, but only 2 are potential blockers: the concern about adding a new page and linking to it from existing pages, and the one where operation is changed to mutation

[sarahxsanders]

@benjie added a commit to build locally for link checking

[sarahxsanders]

hey @benjie just bumping this one for review!

[saihaj]

need to see why the next build is failing here

[saihaj]

I pushed up a commit @sarahxsanders hopefully that fixes failing builds

[saihaj]

CI seems to be passing for our existing actions. We can't really run the new CI jobs from this PR so once we merge will have to see how they do it

[sarahxsanders]

@saihaj feel free to merge this whenever for me! :) I don't have merge permissions (may need to get these for the rest of my incoming PRs as I open them)