cors-plugin per Raghudevan

The add-on has three primary functionalities:
1. A switch to turn it on/off
2. An input field to add Access-Control-Expose-Headers, a list which displays added headers. Default - No extra headers
3. An input field to add a URL/URL pattern to match for while intercepting requests/responses, a list which displays added URLs/URL patterns. Default - Matches all URLs

When turned on, the add-on will intercept all requests/responses from/to the browser and allow cross origin resource sharing requests to the URLs it matches with.