Add language configuration for Cabal files

FIxes #128

Fix tab stop calculation

Fixes re recent API changes

iOS fixes

Update macOS demo screenshot

Fix macOS selection crash and iOS build

* Multi-line selection crashes on macOS if applied to the minimap view. So, we only propagate the insertion point for now.
* iOS flavour catching up on some changes in the macOS flavour.

Update README.md

wibble

Request and merge semantic tokens

This hasn’t been well tested yet.

Contributes to #50

Update README