BNF Parser specification

[andrevidela]

The current idris2 parser has no specification. The first step is to build one to properly track process and completion criteria.

Idris 2 syntax is stateful and therefore cannot be expressed fully using a context-free grammar. However, we can adjust the scope of this task by making operator resolution part of a subsequence desguaring phase, and avoid overloads such as = and **

Even though the parser has a lot of ambiguity built-in, it should be possible to parse raw strings and interporalted string by taking the implementation from Rust Tree sitter (for raw strings) and swift tree-sitter (for interpolated strings)