feat: add `postgres-js` adapter

[smcclure17]

From #386

In src/adapters/adapters.ts: Creates an adapter that mimics the contract/behavior of postgres-js similar to what is done for pg-native.

In src/tests/postgres-js-mimic.spec.ts: Adds tests to verify mimicked behavior matched original.

This only implements the default Sql template tagged literal and unsafe() for performing queries.. We would need to add further implementation to match the features from https://github.com/porsager/postgres