Add stickler-CI to test yaml and mkdown files

[yubiuser]

This adds stickler-CI workflow to lint markdown and yaml files.

Uses https://pypi.org/project/yamllint/ and https://github.com/remarkjs/remark-lint internally

[yubiuser]

This repo needs to be enabled on https://stickler-ci.com/

[PromoFaux]

Did we not already remove stickler at some point in the past?

[yubiuser]

Searching for stickler PRs did not yield any results.

[rdwebdesign]

I think it is enabled now.

[rdwebdesign]

Do you think we need to ignore "vendor" files?

files:
  ignore:
    - '/scripts/vendor/*'

[yubiuser]

It's not complaining now...but maybe does in the future? Shouldn't we report broken styling back to them if errors occur instead of ignoring the files?

[rdwebdesign]

I don't think we should do this for external code.

We can report upstream style issues if we found them, but I don't think this should block/delay a PR.

[yubiuser]

Converted to draft until we figured out why files are not ignored and if we can fix this.

[yubiuser]

The issue is fixed, files are ignored now as they should.
Reason was the leading / in the paths which is removed now.
This was tested on #2239