Create template for popup and forward lyrics to it

[JeremyBarbosa]

After this is merged in, all other work is ready to go:

• The crawler work can be placed in the setLyrics function
• The popup directory controls how the popup looks. It can be treated like any other full page you'd happen to create

To run the extension locally:

• Install Firefox: https://www.mozilla.org/en-US/firefox/new/
• Clone this repo
• Install web ext https://extensionworkshop.com/documentation/develop/getting-started-with-web-ext/
• Cd to ff_extension directory
• Do web-ext run A Firefox window should popup
• Open the browser console (Cmd + Shift + J) https://developer.mozilla.org/en-US/docs/Tools/Browser_Console
• Visit any YouTube video-
• Click the black paw print in top right corner
• Is working if that popup populates with video title