To be fair, most IDEs will usually try to commit their own workspace configurations to a git repo unless you tell them off with a .gitignore. They tend to also exclude themselves from gitignore presets for much the same reason.

VS Code is one notorious offender in that realm; it will try to commit settings.json, even if their gitignore's are set up to ignore all other cruft.

In general, the question of what should go in the source folder is a bit of a mess. Source code, README and License make enough sense, but what about files describing project governance or CI configuration logic? Or what about files that are used to make the forge you're using render the repository in a certain way (for example: bug tracker templates). Those are all cruft insofar that they have nothing to do with code, but it's generally agreed on that you're supposed to commit those, maybe in a dot-folder if necessary.