ci: refresh Serial 0.5.1 README on dependency branch (#8)

Author: LK-Simon

.github/workflows/readme-refresh.yml

@@ -0,0 +1,50 @@
+name: Refresh dependency README
+
+on:
+  push:
+    branches:
+      - feature/8-dependency-refresh-0.5.1
+
+permissions:
+  contents: write
+
+jobs:
+  refresh:
+    if: github.actor != 'github-actions[bot]'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: feature/8-dependency-refresh-0.5.1
+      - name: Refresh current-version documentation
+        shell: python
+        run: |
+          from pathlib import Path
+          path = Path('README.md')
+          text = path.read_text()
+          replacements = [
+              ('ESPNowTransportMonitor\n    - - -> ESPressio ESP-Now >= 0.5.0 < 1.0.0', 'ESPNowTransportMonitor\n    - - -> ESPressio ESP-Now >= 0.5.1 < 1.0.0'),
+              ('Event-backed observation remains a separate opt-in integration in ESPressio Event 5.8.0.', 'Event-backed observation remains a separate opt-in integration in ESPressio Event 5.8.1.'),
+              ('ESPressio Event >= 5.8.0 < 6.0.0\nESPressio Serializable >= 0.10.1 < 1.0.0', 'ESPressio Event >= 5.8.1 < 6.0.0\nESPressio Serializable >= 0.10.1 < 1.0.0'),
+          ]
+          for old, new in replacements:
+              if old not in text:
+                  raise SystemExit(f'missing expected README text: {old}')
+              text = text.replace(old, new, 1)
+          text = text.replace('flowduino/ESPressio-Event@^5.8.0', 'flowduino/ESPressio-Event@^5.8.1')
+          text = text.replace('flowduino/ESPressio-Serial@^0.5.0', 'flowduino/ESPressio-Serial@^0.5.1')
+          marker = 'Historical documentation for earlier release generations remains below where useful.\n'
+          addition = marker + '\nCurrent coordinated dependency baselines for the 0.5.1 release are Units 0.2.2, Timing 2.2.3, Threads 3.1.3, ESP-Now 0.5.1, Event 5.8.1, and Serializable 0.10.1. Command 0.3.0, Security 0.2.0, and Sockets 0.5.0 remain the current optional integration baselines.\n'
+          if addition not in text:
+              if marker not in text:
+                  raise SystemExit('missing historical marker')
+              text = text.replace(marker, addition, 1)
+          path.write_text(text)
+      - name: Commit README
+        run: |
+          if git diff --quiet -- README.md; then exit 0; fi
+          git config user.name 'github-actions[bot]'
+          git config user.email '41898282+github-actions[bot]@users.noreply.github.com'
+          git add -- README.md
+          git commit -m 'docs: refresh Serial 0.5.1 dependency README (#8)'
+          git push origin HEAD:feature/8-dependency-refresh-0.5.1