Function transform

transform(filePath: string, plugin: Plugin): Promise<void>
Given a file path to a css file, this will apply a postcss plugin to transform the file, and write it back to disk.

See the plugin docs for postcss for more information.
Parameters
- filePath: string
  to the file to transform
- plugin: Plugin
Returns Promise<void>
Example
```
import { css } from 'ember-apply';

await css.transform('path/to/file.css', {
  Once(root) {
    root.walkRules(rule => {
      rule.walkDecls(decl => {
        decl.prop = decl.prop.split('').reverse().join('');
      });
    });
  }
});
```
- Defined in css/transform.js:36