Custom dialog for window.ipfs ACLs (make it work under Firefox)

[lidel]

Gist from @alanshaw's TODO list in PR #333 (comment):

• Add a custom confirm dialog. Firefox does not support window.confirm from the background process so it fails - all access to window.ipfs on Firefox will be automatically denied, however as a temporary workaround, Firefox users can use the manage permissions page to enable permissions after they have been auto denied
  • Another reason this is needed is that we want to be able to grant access to all (or a subset of) the API for a given origin, window.confirm can't cover these UX requirements

It may be useful to note how other extensions handle confirmation dialogs (repost from #333 (comment)):

I've noticed and found how Greasemonkey displays confirmation dialog (under Firefox):

https://github.com/greasemonkey/greasemonkey/blob/9ce5dabc74496fa6a631d991302ad4fd80730f1d/src/bg/user-script-detect.js#L76-L99

(HTML page loaded in new browser window with 'type': 'popup')

[lidel]

@alanshaw are you looking into this, or should I mark it as "up for grabs" ?

[alanshaw]

I’m on it tomorrow morn