feat: add types to custom attributes

[ffMathy]

• [X] I have added automatic tests where applicable
• [X] The PR title is suitable as a release note
• [X] The PR contains a description of what has been changed
• [X] The description contains manual test instructions

Changes

The type was missing in the custom attribute definitions. This fixes that. Another PR will come up which builds on this, that starts using it a bit more.

It also removes the prettier check from the tests, as this is now a pre-commit hook. It was so annoying that I couldn't run tests because of formatting. Ran into that a lot. And in the end, it gets formatted anyway.

Test

Automated tests.

[ffMathy]

@jimmycallin has vacation ended yet? 😄

cc @gismya