Suggestion: introduce Contribution Guidlines

[ENDrain]

Since I can't keep but notice some PRs turned down not because of quality of code per se, but due to failure to comply with unspoken contribution standards of this project, which include but are not limited to: commit messages, code styling, naming conventions, commentary or documentation coverage, etc. etc.; with deepest respect to the maintainer of this repository may I suggest introducing contribution guidlines, in a form of CONTRIBUTING.md file, a section in README.md, or any form or shape they find appropriate; in order to prevent any hindrances in acceptance of community contributions in the future.

[ImagicTheCat]

Since you insist on that on multiples PR... e.g. #636.
Those things will not solve magically because I put a CONTRIBUTING.md file. This file is useful for people wanting to read it, not for people trying their best to contribute on a project sometimes without knowing what they are doing because they are learning Lua/git/GitHub at the same time (and I'm fine with that). And the project didn't receive enough contributions to make this mandatory either.

As you can see, people don't necessarily fix what I point out and that's when I have time/will to point it out.