Update on the README file

[osman362]

I have updated the README.md file. The purpose for this is to show those interested how to use tree-sitter.

Instructions are made on:

• how to install and generate tree-sitter
• how to run all unit tests
• how to parse and highlight a specific file

Note: I also did a PR with this and other commits but I only want to merge this because some of the other commits are already in the master branch.