Donations are solicited where they don't belong, and such that they may be taken for mandatory

I couldn't make a merge request to handle this objection I have, so I'm opening an issue.

Today, someone joined #fdroid under the belief that a "fee" (donation) was mandatory for inclusion in F-Droid, concerned that they couldn't pay it.

So I looked at the wording in our Request For Packaging files, and found that indeed it seems very easy to mistake the solicitations to donate as a mandatory part of the process. I think this is not appropriate.

I can imagine other people have shied away, or will shy away, from making a submission without ever joining #fdroid or any place where it could be clarified that donations are optional; so, this issue can have concrete negative consequences.

• At README.md "Make a donation" (not "Consider making", not "Please make") is part of the "Submission queue", together with steps that are actually required.
• While Submission.md and Minimal.md are also mainly requirements for an app to normally be eligible for potential inclusion without any particular issues, the checkbox "Donated to support the maintenance of this app in F-Droid" risks mistaking that for another required step.

In my opinion, these requests should be qualified as optional, and in particular, two actions should be undertaken:

• in README.md "Make a donation" should be changed to "Consider donating", which would clarify it's an optional action;
• any mention of donations should be removed entirely from Submission.md and Minimal.md, which are just a different thing, quite unrelated to donations.

If removing them from the latter is not considered acceptable, then I propose at least changing the wording to "Optionally donated [...]" or "Donated [...] (completely optional)".

While I cannot submit a merge request, I've still made the changes the way I'd make them, in my forked repository, for reference.