1 - [ ] Factorize input size checks (like Parsley's piggy bank).
3 - [ ] Golden tests using more complex grammars.
5 - [ ] Error messages also based upon: [A Parsing Machine for Parsing Expression Grammars with Labeled Failures](https://dl.acm.org/doi/10.1145/2851613.2851750)
7 - [ ] Consider introducing registers like in ParsleyHaskell.
9 - [ ] Concerning the unusual `pure :: H.Term pure a -> repr a`,
10 it may be acceptable to use `H.Term` only internally.
12 - [ ] Move the `Symantic.Univariant.*` modules into a separate package, maybe `symantic-base`.
14 - [ ] `peehole` optimization