"How to contribute" for dummies...

Previous CQUI was abandonned notably because not so many people were involved in its development (and it wasn't easy to start contributing to the project).

I really would like to contribute to the mod. Even if I'm not fluent with the involved languages, I think that many issues can be addressed despite of that. The problem is "I don't know *how* to contribute". Not that I don't know how to use Github, but I don't know how to set a development environment for this mod. RTFM is probably a good answer, but I don't have the time to (1) find and (2) read a lot of (perhaps outdated) documentation on this topic. I believe I'm not alone in that case, and I think it could be interesting to provide some "CQUI contributions for dummies" guideline.

This should ideally include:
1) Links (or a full "tutorial" if you have time) to explain how we can set a development environment for Civilization 6 (I use to play on Windows, but I use to develop on Linux, so the platform is not a big deal).
2) What kind of help do you expect from people? Do you want them to test the latest snapshot to find bugs? Do you want them to fix identified bugs, or to implement new functionnalities? As a proxy for that, you could perhaps add labels to some issues ("need help", "easy to fix", "easy to address", ....)
3) Share your experience in some PR, and add links to them in the readme (or in any "how to contribute" resource). Your experience is probably the most valuable thing we can learn from. Please share it ;-)

Finally, I think it could be interesting to add some information on the Steam page for this mod explaining the development status (ie. can the current version be used to play the game?). First, I think that many players won't come to Github to get this information and will be happy to read it on Steam, and secondly, this will prevent many annoying comments on Steam ;-)

Review the existing README and the Steam page, then identify the current development-environment setup and contribution expectations described in the project. Done means a consolidated contributor guide covers setup, ways to help, example PRs, and current mod status information for Steam users.

Written by the indexing model from the issue text.