Upload to Danbooru

Add a page action and a context menu option (for images) to upload to Danbooru.

Replacement for bookmarklets with better referrer handling. Usage ===== Upload single post via context menu: * Find a picture on the web * Right click on the image * Click Upload to Danbooru Upload post/batch via page action: * Navigate to one of the supported sites * Navigate to the image view page * Click on the Danbooru ("cardboard box") icon on the extensions toolbar Note: Although this extension allows you to upload images from any website, you should be careful to not to upload thumbnail/sample from sites not supported by Danbooru. List of the supported sites can be found here: https://danbooru.donmai.us/static/bookmarklet