Introduce linter & fixer

[easyCZ]

Is your feature request related to a problem? Please describe

Code formatting is hard, tedious and contentious. We want to automatically lint, but more importantly, auto-fix code according to a style.

Initially, can be introduced for TS packages.

Some options:

• pre-commit - recommended
• Prettier
• ...

Describe the behaviour you'd like

• Should run on pre-commit to the repo
• Should run on CI and fail if running the style is non-conformant

[easyCZ]

We're incrementally onboarding packages to this. Closing.