Why not ZetaSQL?

- I started writing this before ZetaSQL was open sourced.

- I wanted to accommodate more dialects of SQL than just ZetaSQL. This would enable translation/analysis/formatting.

- I wanted to provide a starting-point for a developer to make their own -- ZetaSQL is a mature library that is *not* a great place to start hacking something custom.

- I enjoy writing recursive descent parsers and wanted to show how easy it is to do.