Implement ffclipboard

[NotAProton]

NOTICE

I dedicate any and all copyright interest in this software to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

ℹThis PR makes changes to files which aren't auto-updated. Builds will have to be manually submitted to browser stores after merging.

Fixes: #40 (comment)

New API for making bypasses that need cross-domain temporary storage, basically variables that you can use on multiple sites

ffClipboard.set(ID, value)

a = ffClipboard.get(ID)
console.log(a)						// value

ffClipboard.free(ID)
a = ffClipboard.get(ID)
console.log(a)						//null

ffClipboard.get(ID) returns an ffclipboard entry, if id does not exist, returns null
ffClipboard.set(ID, value) sets an ffclipboard entry, if id does not exist, creates it
ffClipboard.free(ID) deletes an ffclipboard entry and frees up storage†, if id does not exist, does nothing

†Chrome limits storage to 5mb

• I made sure there are no unnecessary changes in the code*
• Tested on Chromium- Chrome Windows
• Tested on Firefox

* indicates required