[pg-schema-cli] Support for generating schema of VIEWs

[dantman]

I created a view using PostgreSQL's CREATE VIEW that combines multiple tables in a migration. However it appears that when running pg-schema it does not know that the view even exists and no types are generated.

A VIEW behaves very similarly to a TABLE, responding to the same types of SELECT queries (and possibly UPDATE), so it would be quite helpful if the same type of TypeScript interface was generated for a VIEW as is already generated for a TABLE.