Pull out HTML, CSS and JavaScript scripts from content.js into separate assets

[nickytonline]

Currently JS, CSS and HTML are all built via JavaScript in content.js. To be able to maintain the browser extension code base, separate them into assets of their given type and reference them.

This will allow for contributors to be able to make changes a lot more easily.

[benhalpern]

This works for me as long as it doesn't interfere with the loading in any way. I feel like the way the extension renders before other parts of the HTML is a delicate balance. I assume this is fine but let's make sure this doesn't change behavior.

[Link2Twenty]

Would the files be separate for development but rolled into one file for production?