add reusable workflows

.github/workflows/VerifyDocs.yml

@@ -0,0 +1,56 @@
+name: Verify examples
+
+on:
+  workflow_call:
+    inputs:
+      pyver:
+        description: 'Python version.'
+        required: false
+        default: '3.10'
+        type: string
+
+jobs:
+
+  VerifyDocs:
+    name: 👍 Verify example snippets using Python ${{ inputs.pyver }}
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: ⏬ Checkout repository
+        uses: actions/checkout@v2
+
+      - name: 🐍 Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ inputs.pyver }}
+
+      - name: 🐍 Install dependencies
+        run: |
+          pip3 install .
+
+      - name: ✂ Extract code snippet from README
+        shell: python
+        run: |
+          from pathlib import Path
+          import re
+
+          ROOT = Path('.')
+
+          with (ROOT / 'README.md').open('r') as rptr:
+              content = rptr.read()
+
+          m = re.search(r"```py(thon)?(?P<code>.*?)```", content, re.MULTILINE|re.DOTALL)
+
+          if m is None:
+              raise Exception("Regular expression did not find the example in the README!")
+
+          with (ROOT / 'tests/docs/example.py').open('w') as wptr:
+              wptr.write(m["code"])
+
+      - name: Print example.py
+        run: cat tests/docs/example.py
+
+      - name: ☑ Run example snippet
+        working-directory: tests/docs
+        run: |
+          python3 example.py