fix: keep side effects from modules

[layershifter]

Motivation

Fixes #1189.

Summary

Generally there two kinds of side-effects:

• asset imports (`import './foo.css')
• real code ('import './foo')

We want to keep only imports that contain code. Implemented shouldKeepSideEffect() to check if an import should stay.

shouldKeepSideEffect('regenerator-runtime') // true
shouldKeepSideEffect('./asset.css') // false

The tricky part is that shouldKeepSideEffect('object.values') is false 💥 However, we can't do much at this step: to be sure we need to resolve imports 🙃

Test plan

New tests have been added.

[changeset-bot]

🦋 Changeset detected

Latest commit: 760cb5c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 16 packages

Name	Type
@linaria/shaker	Patch
@linaria/babel-preset	Patch
linaria	Patch
@linaria/testkit	Patch
vite-example	Patch
@linaria/cli	Patch
@linaria/esbuild	Patch
@linaria/rollup	Patch
@linaria/stylelint	Patch
@linaria/vite	Patch
@linaria/webpack4-loader	Patch
@linaria/webpack5-loader	Patch
esbuild-example	Patch
rollup-example	Patch
vpssr-linaria-solid-example	Patch
@linaria/webpack-loader	Patch

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