Make Github Actions configurable to support multiple environments (dev, staging, prod)

[thombergs]

Currently, the cloudformation stacks are only created / updated on push to master.

To test changes in a cloudformation stack, we have to push to master.

Make the deployment scripts configurable so that we can add a name prefix or something, so that we can create the stacks from multiple branches. Each branch would then create its own stacks for testing.