Add @blueprintjs/stylelint-plugin package and no-prefix-literal rule

[p-szm]

Checklist

• Includes tests
• Update documentation

Changes proposed in this pull request:

This PR adds a stylelint rule that bans the usage of .bp3/.bp4 prefixes in favor of using the bp-ns variables. The rule comes with an autofixer that automatically converts the literal prefixes to the bp-ns variable and also inserts the Blueprint variables import.

Screenshot

[adidahiya]

overall looks good! After seeing this rule fixer work in practice, I think we should introduce a more verbose variable which consumers import... $ns feels a little to terse to be littering all over BP consumer code via the autofixer. it could be a simple alias in core/src/common/_variables.scss:

$ns: bp3 !default;
// alias for BP users outside this repo
$bp-ns: $ns;

[adidahiya]

nit: formatting of block comment is slightly off (is the autofixer broken?)

[p-szm]

I fixed this manually, but actually it seems like this is also a valid format and the autofixer always does it this way on my computer. Could you test what happens on your machine?

[p-szm]

It looks like the plugin only inserts starts at the beginning and end https://github.com/Stuk/eslint-plugin-header/blob/66f5269c8a7e3282afd02b914b502f7bb95fe702/lib/rules/header.js#L46

Do you have a template for ts/js files configured in VS code by any chance?

[styu]

@adidahiya i love the idea of introducing $bp-ns or something like that instead of requiring $ns, since the latter is fairly generic in retrospect