Add add_mass_config_trait tool + PyPI auto-publish (v1.2.1) #5

Job	Run time
build (ubuntu-latest, darwin, amd64, ue-cli-darwin-amd64)	16s
build (ubuntu-latest, linux, amd64, ue-cli-linux-amd64)	16s
build (ubuntu-latest, darwin, arm64, ue-cli-darwin-arm64)	19s
build (ubuntu-latest, windows, amd64, .exe, ue-cli-windows-amd64)	50s
build (ubuntu-latest, linux, arm64, ue-cli-linux-arm64)	15s
release	12s
publish-npm	10s
publish-pypi	17s
	2m 35s

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