Allow export/import of options

[digital-carver]

An export (and import) feature would be very useful to keep a backup of the settings, and to transfer them between different Firefox installations/profiles. Especially in the case of different profiles, even Firefox Sync is not an option since usually the point of different profiles is to keep them separate and not sync-ed up to the same Firefox account (in terms of tabs, other extensions, etc.). So for that use case, a json file or something that we can export when we change settings in one profile, and then import from another profile, would be the most flexible and useful feature to have.

[Lej77]

This is a good idea and I will see about implementing it.

[TFWol]

This really needs import/export.

There are at least 17 foldable headers and >110 checkboxes, not to mention the dropdowns and fields you can type in.

It's very tedious changing one option at a time.