refactor(mdx): refactored linting rules and general markdown fixes

[ovflowd]

Description

This PR tackles the remaining MDX/Markdown issues from our repository. Basically, the current sync-api script still had some issues, and some of our Markdown pages are non-conforming, so this PR does the following:

• Reorganises our ESLint configuration to be clean and modularised for each kind of file extension and to use mdx's plugins and parsers for parsing and lining markdown content
• Updates Blog Posts and their Authors (syncing it from nodejs.org)
  • Also fixes the blog syncing script that was partially broken
• Fix our content/** markdown pages by fixing Markdown and MDX issues on them
• Generally fixing our Markdown files
• Applying the new ESLint rules to the source code
• Remove the outdated dependencies and non-used dependencies (decreasing our dependency graph by 20%)
• Removed the Privacy page that should, from now on, redirect to the OpenJS Foundation page, as the privacy.md was gigantic and manually fixing Markdown issues there was not ideal. Also, nodejs.org now redirects users to OpenJS Foundation.

Related Issues

Check List

• I have read the Contributing Guidelines and made commit messages that follow the guideline.
• I have run npm run lint:js -- --fix and/or npm run lint:md -- --fix for my JavaScript and/or Markdown changes.
  • This is important as most of the cases your code changes might not be correctly linted
• I have run npm run test to check if all tests are passing, and/or npm run test -- -u to update snapshots if I created and/or updated React Components.
• I have checked that the build works locally and that npm run build work fine.
• I've covered new added functionality with unit tests if necessary.

[ovflowd]

Note.: Review is better via the Commit tab as file changes are separated by commits. Most of the changes are automated changes by our API script or ESLint.

[nschonni]

This appears to be making some functional changes to the API docs. Might be better to sync the 18.9.0 docs first to minimize the actual diff

[ovflowd]

This appears to be making some functional changes to the API docs. Might be better to sync the 18.9.0 docs first to minimize the actual diff

WDYM? Yes this makes changes to the script that generates docs, and then it also syncs them, as otherwise ESLint would fail 🤔

[ovflowd]

Note.: For some reason build is crashing (locally), I created an issue on upstream: gatsbyjs/gatsby#36599

[codecov-commenter]

Codecov Report

Merging #2757 (846eb4e) into main (fd57b87) will decrease coverage by 1.39%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2757      +/-   ##
==========================================
- Coverage   66.02%   64.62%   -1.40%     
==========================================
  Files         118      122       +4     
  Lines        1351     1405      +54     
  Branches      342      353      +11     
==========================================
+ Hits          892      908      +16     
- Misses        422      461      +39     
+ Partials       37       36       -1     

Impacted Files	Coverage Δ
src/__fixtures__/page.tsx	94.11% <ø> (-5.89%)	⬇️
src/components/Article/index.tsx	100.00% <ø> (ø)
src/components/Banner/index.tsx	100.00% <ø> (ø)
src/components/Codebox/index.tsx	100.00% <ø> (ø)
src/components/EditLink/index.tsx	100.00% <ø> (ø)
src/components/Header/index.tsx	100.00% <ø> (ø)
src/components/Layout/article.tsx	100.00% <ø> (ø)
src/components/NavigationItem/index.tsx	100.00% <ø> (ø)
src/components/SearchBar/index.tsx	52.30% <ø> (-1.03%)	⬇️
src/components/Seo/index.tsx	100.00% <ø> (ø)
... and 46 more

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