Report changes in memory usage that would result from merging a PR

On creation or commit to a pull request, a report of the resulting change in memory usage of the examples will be
commented to the PR thread.

Author: per1234

.github/workflows/compile-examples.yml

@@ -23,6 +23,9 @@ jobs:
     name: ${{ matrix.board.fqbn }}
     runs-on: ubuntu-latest
 
+    env:
+      SKETCHES_REPORTS_PATH: sketches-reports
+
     strategy:
       fail-fast: false
 
@@ -49,4 +52,12 @@ jobs:
             # See: https://github.com/arduino/compile-sketches#libraries
           sketch-paths: |
             - examples
+          enable-deltas-report: true
+          sketches-report-path: ${{ env.SKETCHES_REPORTS_PATH }}
 
+      - name: Save sketches report as workflow artifact
+        uses: actions/upload-artifact@v2
+        with:
+          if-no-files-found: error
+          path: ${{ env.SKETCHES_REPORTS_PATH }}
+          name: ${{ env.SKETCHES_REPORTS_PATH }}

.github/workflows/report-size-deltas.yml

@@ -0,0 +1,24 @@
+name: Report Size Deltas
+
+# See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
+on:
+  push:
+    paths:
+      - ".github/workflows/report-size-deltas.yml"
+  schedule:
+    # Run at the minimum interval allowed by GitHub Actions.
+    # Note: GitHub Actions periodically has outages which result in workflow failures.
+    # In this event, the workflows will start passing again once the service recovers.
+    - cron: "*/5 * * * *"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  report:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Comment size deltas reports to PRs
+        uses: arduino/report-size-deltas@v1
+        with:
+          # The name of the workflow artifact created by the sketch compilation workflow
+          sketches-reports-source: sketches-reports