Create sqlite index tables from JSONSchema definitions in @mapeo/schema

[gmaclennan]

We need a way to generate sql CREATE TABLE statements based on the JSONSchema definitions (only top-level properties - nested props to be stored as JSON in SQLite).

We can generate SQL statements ourselves from JSON Schema to generate extraColumns, or we can use a helper like Drizzle-kit, which also gives us added benefits of typed sql select statements. Drizzle provides a nice API for this. I think it will be easier to map our JSOn schema to the drizzle table schema API than it would be to generate CREATE TABLE SQL statements manually from JSON Schema.

See #135

This will also give us typed db.select() functions for our datatype API, which will give a bit more typesafety for that part of the code.