feat: make @linaria/shaker optional

[kazuma1989]

Motivation

I want to use Linaria without evaluating the interpolated values. So I don't need to install @linaria/shaker but @linaria/babel-preset requires the package if no evaluator rules are active.

The default evaluator rules will be skipped when any rules option is set. It makes @linaria/shaker optional.

Related #813.

Test plan

A rollup example. This should work without @linaria/shaker installed.

import linaria from '@linaria/rollup';

export default {
  plugins: [
    linaria({
      rules: [],
    }),
  ],
};

[callstack-bot]

Hey @kazuma1989, thank you for your pull request 🤗.
The coverage report for this branch can be viewed here.

[Anber]

Thank you @kazuma1989!

[steffenmllr]

@Anber any chance this get's published on npm?