Add add-on ID to persist options when temporarily loading add-on

[mcomella]

e.g. https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/WebExtensions_and_the_Add-on_ID#When_do_you_need_an_add-on_ID

[mcomella]

This may not be possible: users already have the auto-generated add-on ID which might prevent us from specifying one manually.