We should run `ng build --configuration production` in github actions

[Jane Sandberg]

Right now, a committer can do the following:

1. Run `ng build`
2. Put the code through its paces, run tests, etc.
3. Forget to also run `ng build --configuration production`
4. Think everything is fine and merge the code.

...and then it turns out that the code doesn't compile with --configuration production, and we can't release or build from source.

Similar to our other github actions, we should add one that checks if ng build --configuration production succeeds, so we can see quickly if the client compiles or not. :-)