Building this reposotiry

[kb2623]

Hi, I have some suggestions:

1. Please add some information on how to build this project for testing. I suggest a new markdown file for just that.
2. For build this project a makefile can be used.
3. From which directory do I have to run scripts in tools directory?
4. Script import-crowdin.sh in tools should download the needed files or even better, you can just include needed files in the repository.
5. Some sripts in tools directory need some arguments. It would be nice to have some default values for them.
6. I must say that I a new to developing extensions for browsers, so maybe add some information somewhere on where to start.

I really like uMatrix extension and I do not want to switch to NoSript, because it is missing functionality that uMatrix has and therefore I must install some more extensions just to get the same power that uMatrix has. Maybe this will be a go to extension for me when uMatrix looses its support in newer versions of Firefox.