PostCSS URL rebase plugin

[PostCSS] plugin for rebasing URLs to a given root URL.

[PostCSS]: https://github.com/postcss/postcss

``css
.foo {
/ Input example /
background: url("images/test.jpg");
mask: url("/images/layout/shape.svg");
}
`

`css
.foo {
/ Output example /
background: url("https://example.com/images/test.jpg");
mask: url("/images/layout/shape.svg");
}
`

Usage

Step 1: Install plugin:

`sh
npm install --save-dev postcss postcss-urlrebase
`

Step 2: Check you project for existed PostCSS config: postcss.config.js
in the project root, "postcss" section in package.json
or postcss in bundle config.

If you do not use PostCSS, add it according to [official docs]
and set this plugin in settings.

Step 3: Add the plugin to plugins list:

`diff
module.exports = {
plugins: [
+ require('postcss-urlrebase')({ rootUrl: "https://example.com/wp/wp-themes/example/" },
require('autoprefixer')
]
}
`

$3

#### rootUrl (_required_)
The root URL to which the existing URLs should be based to.

#### skipHostRelativeUrls (optional (default: true))
Should already host-relative URLs (as /images/test.jpg (URL starts with /`)) be skipped?

[official docs]: https://github.com/postcss/postcss#usage