See the contributing section in the readme for more detailed guideline: https://github.com/Helium314/HeliBoard?tab=readme-ov-file#guidelines
tl;dr (you should still read the full list though):
* make sure it's wanted
* a single thing only
* describe it properly
* re-use existing mechanisms / code
* low performance impact
* make it a draft if you still want to work on it
* don't do translation PRs

Further
* When the PR contains "fixes" <issue number>, the related issue will be linked and automatically closed if the PR is merged (also works for other words like "fix", "resolve", "resolves", "closes", ...)
* If you add a keyboard layout, make sure you have read https://github.com/Helium314/HeliBoard/blob/main/layouts.md#adding-new-layouts--languages
* Please avoid force-pushing when doing changes. This way it's not possible which parts have changed since the previous state.