Allow setting up phabricator from container

[eeejay]

Fixes #8

Not very pretty, but it does the job!

[Rob--W]

Using webRequest to copy/paste headers defeats containers.

If all you want is to make a request in a specific container, currently the best option is to open a (background) tab in that container (could be an extension tab) and send a request from there. That is the least bad way, until a first class feature exists (https://bugzilla.mozilla.org/show_bug.cgi?id=1670278).

P.S. the webRequest-based approach was mentioned before (with code snippet) at #8 (comment)

[eeejay]

Thanks, I was looking into this. When you say "open a (background) tab", do you mean a visible non-active tab, or somehow a hidden one? I can't find a way to do the latter, and the former method has some risk since it can interfere with other tab management extensions, and generally be confusing to the user.

[Rob--W]

I meant browser.tabs.create with active:false to open a visible tab in the background.

The latter is also possible, with the browser.tabs.hide() and the tabHide permission. But that requires an additional user opt in, once.