Add support for Dynamic Type, allow to increase user interface font

[anthonypkeane]

Make the app to support dynamic type, the user can change their font in settings then the UI should follow it.

[iccub]

This is possible in reader mode at the moment

[anthonypkeane]

True, but needed on all site IMO without the need for reader mode

[iccub]

This is the ticket for user interface font size aka dynamic type,
For website font size please check #3222

I also think this ticket should be split in multiple smaller tickets, basically each part of the interface can be updated separately

[iccub]

closing, we will use smaller tickets for each area we want to improve