Typing and fstrings

[JedMeister]

General typing and fstring updates. This is currently untested and likely incomplete.

This is #15 - rebased on current master - https://github.com/turnkeylinux/fab/commit/998de3b2800843fd29e20334d2e1df5c3431cae6

It was previously merged into #16 - but has been separated again as it's non arm64/rpi specific.

A separate arm64/rpi specific PR can be found as #27