feat: add no-missing-atx-heading-space rule

[SwetaTanwar]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

This PR adds a new rule no-missing-atx-heading-space to ensure there is a space after hash on ATX style headings in Markdown

What changes did you make? (Give an overview)

Added the no-missing-atx-heading-space rule, along with documentation and tests.

Related Issues

fixes #370

Is there anything you'd like reviewers to focus on?

Screenshots

[lumirlumir]

Could you please take a look at the CI failures?

I think there might be some edge cases that were missed.

[SwetaTanwar]

Could you please take a look at the CI failures?

I think there might be some edge cases that were missed.

Fixed the edge case for markdown lint 0a7f1ec

[nzakas]

How about no-missing-atx-header-space? I think reads a bit clearer.

[SwetaTanwar]

How about no-missing-atx-header-space? I think reads a bit clearer.

Agreed, updating the rule name to no-missing-atx-header-space

[lumirlumir]

Would it be better to use no-missing-atx-heading-space?

CommonMark Spec and Mdast use heading.

• https://spec.commonmark.org/0.31.2/#atx-headings

[nzakas]

@lumirlumir yes, good call. We should use "heading" instead of "header".

By the way, you don't have to set assignees on PRs. it's assumed the author is the assignee.

[SwetaTanwar]

@lumirlumir I have addressed your feedback, PTAL

[lumirlumir]

@SwetaTanwar

I apologize if my review comments came across as a bit aggressive. My English is still a work in progress, so there may have been some unintended tone. I’ll make sure to use kinder wording next time.

I’ll review it in a few days — thank you in advance for your patience!

[SwetaTanwar]

@lumirlumir, No worries at all — I didn’t find the tone off in any way. Really appreciate your comments, they helped catch some important cases I missed.

Looking forward to your next round of feedback when you get a chance! 😊

[lumirlumir]

LGTM! Thanks for your hard work and patience on this PR.

Would like to ask @snitin315 and @nzakas to re-verify before merging.

[snitin315]

LGTM, thank you for contributing ⭐