Fix Docker build and improve checks #220

This commit improves multiple aspects of Docker builds:

- Enable artifact output validation for Dockerfile.
- Correct the path references in Dockerfile for the distribution
  directory.
- Add Dockerfile specific indentation rules to `.editorconfig`.
- Use `npm run install-deps` for dependency installation, enhancing
  build reliability.
- Add automation script `verify-web-server-status.js` to verify running
  web server on given URL.
- Introduce automated build verification for Dockerfile:
  - On macOS, install Docker with colima as the container runtime
    because default agents do not include Docker and Docker runtime is
    not installed due to licensing issues (see actions/runner-images#17).
  - On Windows, there's no Linux container support (actions/runner#904,
    actions/runner-images#1143), so keep the checks for macOS and Ubuntu
    only.

.github/workflows/checks.build.yaml

@@ -1,4 +1,4 @@
-name: build-checks
+name: checks.build
 
 on:
   push:
@@ -68,3 +68,33 @@ jobs:
       -
         name: Verify bundled desktop build artifacts
         run: npm run check:verify-build-artifacts -- --electron-bundled
+
+  build-docker:
+    strategy:
+      matrix:
+        os: [ macos, ubuntu ] # Windows runners do not support Linux containers
+      fail-fast: false # Allows to see results from other combinations
+    runs-on: ${{ matrix.os }}-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Install Docker on macOS
+        if: matrix.os == 'macos' # macOS runner is missing Docker
+        run: |-
+          # Install Docker
+          brew install docker
+          # Docker on macOS misses daemon due to licensing, so install colima as runtime
+          brew install colima
+          # Start the daemon
+          colima start
+      -
+        name: Build Docker image
+        run: docker build -t undergroundwires/privacy.sexy:latest .
+      -
+        name: Run Docker image on port 8080
+        run: docker run -d -p 8080:80 --rm --name privacy.sexy undergroundwires/privacy.sexy:latest
+      -
+        name: Check server is up and returns HTTP 200
+        run: node ./scripts/verify-web-server-status.js --url http://localhost:8080