Dependabot, update actions

Signed-off-by: Sara Damiano <sdamiano@stroudcenter.org>

.github/dependabot.yml

@@ -0,0 +1,10 @@
+version: 2
+updates:
+  - package-ecosystem: 'github-actions'
+    directory: '/'
+    schedule:
+      interval: 'daily'
+    labels:
+      - 'CI/CD'
+    commit-message:
+      prefix: ci

.github/workflows/build_examples_platformio.yaml

@@ -54,7 +54,9 @@ jobs:
           fi
 
       - name: Set up Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.x'
 
       # This should be pulled from cache, if there's not a new version
       - name: Install PlatformIO