Icon overhaul

[whyboris]

Problem: currently we're reusing several icons as we've run out of available ones in the font file. We'll be adding more settings in the future, and it's great not to have to rebuild the icon font every time a new icon is added.

Solution: start using svg files directly (instead of a custom font that needs to be generated from the pre-made svg files).

I'll be happy to take on the task - closer to when we need to release v2.0 👍

[whyboris]

This seems more and more pressing 😅 - we have so many new buttons, and this must be ready by release and it will take some time to craft new icons.

I'll work on this next 🏃

[whyboris]

Will be closed with #113 🎉