Please add pkg-config support for use with GNU AutoTools (was #237 not merged by mistake?)

### 🤔 What's the problem you're trying to solve?

GNU AutoTools refuses to identify cucumber-cpp as installed because it doesn't install .pc files. There was a PR for this (#237) in 2019 that appeared to have been approved for inclusion, but never got merged into main. Was this PR discarded in error?
/

### ✨ What's your proposed solution?

Either

- explain why cucumber-cpp should not support GNU AutoTools
- explain why #237 was incorrect, abandoned or otherwise **or**
- merge #237 into `main` and initiate a 0.8.0 release in the near future after sufficient testing, and inclusion of any other pending features.

### ⛏ Have you considered any alternatives or workarounds?

I could write my own upstream *.pc files, but this seems like an inferior solution to including them upstream.

### 📚 Any additional context?

I'm really looking for an explanation of why #237 was closed, and if it was closed in error.