Stale pull requests: Review, test and maintain PRs

[ann0see]

Currently there are many open Pull Requests (some almost finished, some just needing a second review,...) which are stale. @softins and @pljones are mainly reviewing the PRs on the main repo, while @gilgongo and @ignotus666 are doing this for the website. Often there's missing a second review and "force merges" without a second approval are necessary. Due to the lack of time, I can't test the PRs in deph and follow the community closely, that's why I would highly appreciate some more members of the community helping out with reviewing, testing (and maintaining pull requests).

Everyone using Jamulus can test the changes from the pull requests by installing the binaries created on every Pull request. Just click on checks>Auto-Build and test the generated assets. Moreover, language PRs are easily reviewable (check for spelling mistakes, syntax errors,...).

@jamulussoftware/maindevelopers feel free to comment/edit my post if you have any ideas.