feat: Add option to create isolated virtual environment in Python setup action

.gitea/actions/setup-python-env/action.yml

@@ -26,6 +26,10 @@ inputs:
     description: Execute setup script dry run before live run when true.
     required: false
     default: 'true'
+  create-venv:
+    description: Create an isolated virtual environment when using the system Python.
+    required: false
+    default: 'false'
 runs:
   using: composite
   steps:
@@ -48,7 +52,7 @@ runs:
         python -m pip --version >/dev/null 2>&1 || python -m ensurepip --upgrade
         python -m pip --version
     - name: Create virtual environment
-      if: ${{ inputs.use-system-python == 'true' }}
+      if: ${{ inputs.use-system-python == 'true' && inputs.create-venv == 'true' }}
       shell: bash
       run: |
         set -euo pipefail