Google Docs Show Image Source

Show the original image source for google doc images.

Adds links to view or copy the original images used in a google doc. This extension is tied pretty closely to the current implementation of google docs. Therefore, this extension is likely to break. If this happens please file an issue on github: https://github.com/jeremypepper/google-doc-image-links-extension/issues and I'll try to fix it asap.