ReactPeg: Declarative parser generator based on PEG.js

Now, we can generate parser in "react" style: declarative & composable:

• playground: https://mistlog.github.io/react-peg-playground/
• docs: https://mistlog.github.io/react-peg-docs/docs/getting-started
• template project: https://github.com/mistlog/react-peg-template