ci: add GitHub Action and Markdown linter

[nathan-weinberg]

This is a meta-linter of sorts that lints GitHub Actions themselves

Should be useful when we introduce more CI to this repository

[nathan-weinberg]

@mairin @connor-leech @jjasghar @sstano Hey y'all, I've added this GHA linter and fixed some linting issues but it did require changing the existing nextjs action - is there a way I can test if I broke any functionality or not? Last thing I want to do is set y'all back with this

[nathan-weinberg]

Will hold off on merging until I know I won't break the website deploys 😄

[joesepi]

LGTM but I will check with @mscherer to plan to test it.

[mscherer]

I am very much in favour of this, but given that we already struggle a bit with the regular linter, I would prefer if that's applied after Summit. (and the current PR can't be merged as we changed the SECURITY.md file)

[nathan-weinberg]

@mscherer we can definitely hold this, no rush to do this before Summit

[nathan-weinberg]

@mscherer can we revisit this now that Summit is over?

[nathan-weinberg]

Rebased but I still need to harden these actions per @bjhargrave's examples in other repos

[bjhargrave]

You also need to include .github/dependabot.yml to manage the actions.

See https://github.com/instructlab/.github/blob/main/.github/dependabot.yml

You should add a section to the dependabot config to handle the JS/yarn dependencies.