Add redshiftserverless.py module

[tnielsen2]

• Add redshiftserverless.py module to support the deployment of Serverless Redshift Workgroups and Namespaces.
• Update CONTRIBUTING.md to
  • remove invalid --name argument and remove --stub arguments from example gen output. --name is not a valid arg in conjunction with -- stub, and using --stub results in incomplete autogenerated python modules from ResourceSpec that will not pass tests.
  • spelling fixes

[markpeek]

@tnielsen2 I'll have to review my contributing guides but I think you've figured it out. Basic flow is:

# download latest spec files
make spec
# generate the new troposphere file
./scripts/gen.py redshiftserverless > troposphere/redshiftserverless.py
# do black and isort fixups
make fix

[tnielsen2]

Thanks @markpeek!

[markpeek]

Oh, and I should add running:

# run tests
make test
# run the linters
make lint

[tnielsen2]

I had issues running make lint test on my machine. Namely because I was missing NPM/NPX and due to another (likely) venv issue. I don't recall seeing any info on NPM as a pre-req for this, but I figured I would mention it anyway!

[markpeek]

Thanks!