Add SQL function to create geom/datetime indexes when creating a new Table in the public schema

eoAPI is built on top a Postgres database that has a pgSTAC schema but also a public one we can use to store other geo data. We don't have a service to ingest data but I think it will be cool to create a simple SQL script to automatically create INDEX on any geometry and datetime column so `eoapi.vector` is fast.

```sql
CREATE OR REPLACE FUNCTION on_create_table_func()
RETURNS event_trigger AS $$
BEGIN
-- find geom/datetime column
-- add indexes
END
$$
LANGUAGE plpgsql;

CREATE EVENT TRIGGER
on_create_table ON ddl_command_end
WHEN TAG IN ('CREATE TABLE')
EXECUTE PROCEDURE on_create_table_func();
```

The function and trigger should be used in https://github.com/developmentseed/eoAPI/blob/019e4b56cbfe5919883833a3656c28ba6ad3375e/infrastructure/aws/handlers/db_handler.py#L268

cc @bitner