Implement conditional Python requirements installation

Add conditional installation of Python requirements if specified.

Signed-off-by: Dave Fisher <dave2wave@comcast.net>

Author: dave2wave

pelican/action.yml

@@ -111,6 +111,11 @@ runs:
     - name: Generate website from markdown
       shell: bash
       run: |
+        if [ -n "${{ inputs.requirements }}" ]
+        then
+          echo "Installing python requirements from ${{ inputs.requirements }}"
+          PIP_BREAK_SYSTEM_PACKAGES=1 pip3 install -r ${{ inputs.requirements }}
+        fi
         if [ "${{ inputs.debug }}" == 'true' ]
         then
           OPTS='-D'