ci: add snap workflows

.github/workflows/close-snap.yml

@@ -0,0 +1,19 @@
+name: Close Snaps
+
+on:
+  pull_request:
+    types: [closed]
+
+jobs:
+  close:
+    runs-on: ubuntu-latest
+
+    timeout-minutes: 5
+
+    steps:
+    - name: Close obsolete channels
+      uses: canonical/actions/close-snap@release
+      continue-on-error: true
+      with:
+        channel: edge/pr${{ github.event.number }}
+        snapcraft-token: ${{ secrets.SNAPCRAFT_TOKEN }}

.github/workflows/snap.yml

@@ -0,0 +1,34 @@
+name: Snap
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+
+jobs:
+  Snap:
+    runs-on: ubuntu-latest
+
+    timeout-minutes: 45
+
+    strategy:
+      matrix:
+        platform:
+        - amd64
+        - armhf
+        - arm64
+        # Broken dependencies: - ppc64el
+        # Broken environment: - s390x
+
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v3
+      with:
+        fetch-depth: 0  # needed for version determination
+
+    - name: Build and publish the snap
+      uses: canonical/actions/build-snap@multiarch
+      with:
+        architecture: ${{ matrix.platform }}
+        snapcraft-token: ${{ secrets.SNAPCRAFT_TOKEN }}
+        publish: ${{ github.event_name == 'pull_request' && github.repository == github.event.pull_request.head.repo.full_name }}
+        publish-channel: edge/pr${{ github.event.number }}