Move local_sql_syntax from valve.rs to this project

[jamesaoverton]

The first feature I'd like this library to have is this code for abstracting over the differences in SQLite and PostgreSQL binding strings:

https://github.com/ontodev/valve.rs/blob/main/src/lib.rs#L1106

[lmcmicu]

Implemented. See the commit: 8bb5e98 and also the corresponding commit in valve.rs: ontodev/valve.rs@67f8c6f