feat(linter): implement import/extensions

[taearls]

Added the rule for import/extensions from the eslint-plugin-import package.

I ported the tests from https://github.com/import-js/eslint-plugin-import/blob/main/tests/src/rules/extensions.js, which needed to be done manually because the rule generation script did not work for me.

One difference between my tests and theirs is that their tests occasionally will pass eslint configuration settings on a per test basis. For our purposes, this didn't seem necessary, because we just need to pass the rule-specific configurations.

I categorized this rule as performance in light of this recommendation from the Vite docs: https://github.com/import-js/eslint-plugin-import/blob/main/tests/src/rules/extensions.js

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #11548 will not alter performance

_{Comparing taearls:tyler/import/extensions (d870279) with main (4ca659c)}

Summary

✅ 38 untouched benchmarks

[camc314]

I categorized this rule as performance in light of this recommendation from the Vite docs: https://github.com/import-js/eslint-plugin-import/blob/main/tests/src/rules/extensions.js

I changed the category to restriction, as I think as:

1. having a config of never would make the perf slower?
2. forcing the file extension can be confusing when using ts, e.g. to i use the TS extension, and have it transformed to the JS at build time, or do i use the js extension, as that will be the extension of the TS file at runtime?

[camc314]

thank you!

[taearls]

I categorized this rule as performance in light of this recommendation from the Vite docs: https://github.com/import-js/eslint-plugin-import/blob/main/tests/src/rules/extensions.js

I changed the category to restriction, as I think as:

1. having a config of never would make the perf slower?
2. forcing the file extension can be confusing when using ts, e.g. to i use the TS extension, and have it transformed to the JS at build time, or do i use the js extension, as that will be the extension of the TS file at runtime?

Yeah that's a valid point, makes sense.