chore: Add action to test build the snap

Consistent with my other snaps.

.github/workflows/test-snap-can-build.yml

@@ -0,0 +1,22 @@
+name: 🧪 Test snap can be built on x86_64
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: snapcore/action-build@v1
+        id: build
+
+      - uses: diddlesnaps/snapcraft-review-action@v1
+        with:
+          snap: ${{ steps.build.outputs.snap }}
+          isClassic: 'false'