docs: Use link to tagged version for rule docs

[sudo-suhas]

What is the purpose of this pull request?

Documentation update

What changes did you make? (Give an overview)

This adds a helper to lib and uses the version present in package.json for generating the URL to tagged version of the rule documentation. I think this is good because the documentation will match the version the user has installed. This way, even if a rule is changed or removed in the future, the user can find the documentation with ease.

Note: The rule eslint-plugin/require-meta-docs-url cannot be used with a function which would return the URL(see not-an-aardvark/eslint-plugin-eslint-plugin#58) so I have disabled it.

[macklinu]

@sudo-suhas thanks for contributing and for the helpful PR description!

As a whole, I like this change. However with <=v3.6.0 of eslint-plugin-promise, there were inconsistencies with rule documentation URLs in the README. Some of the URL headings were just the rule name, whereas other URL headings were Rule: {{ruleName}}.

I think a change like this will be useful for v3.7.0 (next version of eslint-plugin-promise) and onward. I'm not really sure how to support older versions of documentation URLs with inconsistencies without adding specific checks to the getDocsUrl() function when the version is <=v3.6.0, or if that would be worth doing/maintaining.

It's something I'd like to think about a little bit more. Please let me know if you have more thoughts around this. Also, thanks for opening and linking to eslint-community/eslint-plugin-eslint-plugin#58 - I had the same question the other week!

[sudo-suhas]

Regarding the URL headings of format Rule: {{ruleName}}, I saw this as well. But this is not something we need to worry about because the changes in this PR only affect future versions. The past v3.6.0 version is immutable and won't be affected(the tagged version doesn't have docs URL itself). Even if we were to update the getDocsUrl function, that will never make it through to older versions.

[macklinu]

You make a good point, was definitely overthinking this before. LGTM, thanks again!