Instructions on how to build Codexia are missing in README

[alilosoft]

I'm really new to Ruby ecosystem, and wanted to contribute to Codexia, I've figured out how to make some obvious changes, but I don't know how to run the build locally and what are the tools needed for that, so it would be great to have some instructions in the README file on how to do that.
Note: I'm using a Windows 10 machine, but if the build could be done in Docker that also fine.

[0crat]

@yegor256/z please, pay attention to this issue

[yegor256]

@fellahi-ali I made some changes, try now... 59a54cf