keep ARM json up-to-date by building Bicep on successful merges to main

**Is your feature request related to a problem? Please describe.**

We have to remember to manually build the ./mockSpacestation.bicep file whenever we change the implementation so that the compiled ./mockSpacestation.json file is available for Portal deployment and for users without Bicep.

That's silly. We should automate that.

**Describe the solution you'd like**

Whenever something is approved to merge to main, we should build ./mockSpacestation.bicep so that ./mockSpacestation.json always reflects what's in the repo.

**Describe alternatives you've considered**

Remembering to manually build and inspect ./mockSpacestation.json for validity before pushing up a PR.

**Additional context**

n/a