This project is NOT open for direct contributions (you may still
contribute by providing patches for download somewhere else for
example).

You still can open a PR if you like. But it may not be accepted, or even
just ignored.

If a PR is accepted or not solely depends on this repos owners opinion.
There are NO objective "rules" or similar that could be fulfilled for a
PR to get merged. It only gets merged if the repo owner thinks he should
merge it.

For example there are neither any formatting rules nor is there any
definition of what kind of changes are allowed at all in this project.
(As already said) this solely depends on the repo owners opinion and
also facts that are a pro do NOT change that.

Be aware that opinions are no hard rules. Therefore they can change at
will. Only because a similar decision was made earlier, does not mean
that now a similar approach is acceptable.

Further, the repo owner may apply any changes of any kind before or
after merging a contribution.

If a PR does not get merged, it is recommended to publish your work as
patch files somewhere outside this repository.