Install shiny before shinylive in GHA

Author: wch

.github/py-shiny/setup/action.yaml

@@ -25,6 +25,10 @@ runs:
         shell: bash
         run: |
           pip install https://github.com/rstudio/py-htmltools/tarball/main
+          # Install shiny _before_ shinylive; otherwise shinylive will install cause
+          # shiny to be installed from PyPI, and may bring in old versions of
+          # dependencies.
+          pip install -e .
           pip install https://github.com/posit-dev/py-shinylive/tarball/main
           make install-deps