Automatically detect if no programming language is present to show overview in data-only repository

Hi!

Summary 💡

Even in repositories where there are no programming languages (e.g. https://github.com/LemmyNet/lemmy-ansible) but only data/configuration, by default you get this:

Error: Could not find any source code in this repository

Maybe in such cases it shouldn't ignore non-programming languages and produce an error output, but fall back to the other most prevalent language.

Motivation 🔦

Related to https://github.com/o2sh/onefetch/issues/1208.
I didn't know right away how to make YAML appear and I was confused because I saw that it was supported as a language, then I found that issue and understood, but it wasn't very intuitive.

Maybe it is also worth reopening that issue, I think an improvement there could be to enrich this error message with suggestions, like:

Error: Looking for programming language source code, but couldn't find any in this repository
       You can add the option `-T data/markup/...` to show the repository overview regardless

Or even better, based on the content of the repository, it could suggest which argument to provide to the -T option, though, if it's able to do that, it would probably be better to just do it without further user intervention, which falls back into this issue (idk, I'm confused because I'm not aware of all the possibilities)

The issue names no files or tests. First locate the language-detection path and the -T option handling in this CLI, then reproduce the error with a data-only repository such as LemmyNet/lemmy-ansible. Before implementation, clarify whether completion means automatic fallback, an improved suggestion, or both, and verify that the chosen behavior shows the repository overview.