The parser for the handlebars-language (work in progress)

1. Write a framework for parser tests (partially done)
2. Write parser tests to cover all relevant template variations, using the current parser as reference
3. Implement a parser

The parser should not be based on jison but use plain TypeScript. Debugging jison was a pain in the past and I think that by writing it without a framework, it can be made cleaner and better debuggable.

A complete set of tests will also enable other people to write their own parsers that are possibly faster than this one.

• Clean code, easy to understand code
• Size does not matter that much here. In my opinion, there are few use-cases for using the parser itself in the browser. Parsing and compiling templates is usually done in a Node.js environment. It makes sense not to use too many large dependencies, but we don't need to save every byte possible in the final build artifact.
• Performance is an issue, but not the primary one at the moment. Optimizations can be done later.