[HTTPS-Everywhere] Mozilla moving to new WebExtensions API

[Jacob Hoffman-Andrews]

According to this Mozilla blog post, Firefox is moving to a new
WebExtensions model, which is supposed to be compatible with Chrome
extensions:
https://blog.mozilla.org/addons/2015/08/21/the-future-of-developing-firefox-add-ons/.

We have a long lead time before XPCOM is deprecated, and there are some
big issues to solve, like how to make SSL Observatory work in such a
world (probably we need Mozilla to implement some extra APIs).

We should try implementing HTTPS Everywhere using the new API, to see if
it is possible. Probably starting from the Chromium code rather than the
existing Firefox code makes the most sense.

(text copied from: https://github.com/EFForg/https-everywhere/issues/2640)

If anyone would like to volunteer to try this, it would help provide
early feedback to Mozilla on the viability of the new model.