Move away from using chrome commands

[RealP]

Issue

Currently we use chrome commands to capture keyboard events and inject actions in the background script. This has the limitation of not allowing more the 4 keyboard shortcuts to be set by default.

While we can add as many shortcuts as we want using this method, the fact that some are not set by default is confusing.

Possible Solutions

1. Event listeners could be adding in the contentScript.js. Similar to how Alt+Click works today.