fix(docs): Update markdown processor to use GFM

[charlottetan]

What does this PR do?

Improve repo: Update the markdown processor to use GFM instead of the default (kramdown). GFM is the processor Github uses. Resolves #5559.

Docs for more information:

https://docs.github.com/en/pages/setting-up-a-github-pages-site-with-jekyll/setting-a-markdown-processor-for-your-github-pages-site-using-jekyll

Examples here:

https://charlottetan.github.io/free-programming-books/CONTRIBUTING-fa_IR.html

https://charlottetan.github.io/free-programming-books/HOWTO-fa_IR.html

For resources

Description

Why is this valuable (or not)?

How do we know it's really free?

For book lists, is it a book? For course lists, is it a course? etc.

Checklist:

• Read our contributing guidelines
• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction)

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!

[davorpa]

❗ Update pr title with scope fix(docs): ....

ℹ️ remove non scoped tasks

[davorpa]

More docs about GMF & Kramdown: https://jekyllrb.com/docs/configuration/markdown/#commonmark

🆗 I have not seen any other listing break.

[davorpa]

Ready to merge 🎆 🎉

Thanks for your valuable researches

[eshellman]

Awesome teamwork