Support multiple schemas, similar to multiple tables

[RickeyWard]

Allow passing multiple -s and generating several schemas at once into the same file, similar to the table flag. currently have to run the command multiple times for different schemas and since they aren't aware of each other can sometimes cause issues.

possible issue not directly related but could be solved with this feature:
this could be a bug in type generation, where its seeing the type but not finding it in other schemas (just creates a ts file with errors) but if I could just generate -s public -s custom, they would be in the same fine and it would be fine. Not sure which is correct.