Option to migrate create without down.sql

[weeco]

Is your feature request related to a problem? Please describe.
I'm always frustrated when migrate create creates an up and down sql even though I decided to not use down migrations at all.

Describe the solution you'd like
An option that allows us to disable the generation of the down sql file.

Describe alternatives you've considered
Delete the generated down sql file every time after I ran the create command.

Additional context