Add right-click menu

[stackxp]

This adds a right-click menu to copyparty allowing you to:

• Open files in different ways (Open in MD editor, Play video as audio, etc.)
• Cut, Copy, Paste and Delete stuff
• Download files normally or as an archive
• mess with selections

Apart from that, this also:

• Adds a new section to the options page
• Allows you to use the regular right-click menu when double right-clicking
• Adds 19 new translation keys

I didn't implement the grid view yet but I hope that isn't a problem :)

(This PR complies with the DCO; https://developercertificate.org/)

[9001]

nice!! struggling to even find nitpicks, this is dope :grin:

only thing is the use of let rather than var, do you think a find/replace to use var instead would cause issues? ah, I guess let fn = function() {}; would need to be scoped inside an iife or something... (sorry)