Cover the pip install . use case in GitHub Actions

[riley-harper]

Currently our GitHub Actions install hlink in editable mode with the -e flag and with additional development dependencies. We need to install the development dependencies for linting and testing, but we could probably get away with not passing the -e flag to pip install. This might help prevent some installation bugs where pip install .[dev] doesn't copy over needed resource files. We ran into one of these bugs recently with Jinja.

We may also want to set up some GitHub Actions that just run pip install . without installing development dependencies and then confirm that some of the basics of hlink are working as expected. pytest won't be installed in this situation since it's a development dependency.