ci: run on all platforms, install sys deps

.github/workflows/test.yml

@@ -19,11 +19,22 @@ concurrency:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ['windows-latest', 'macos-latest', 'ubuntu-latest']
+
+    runs-on: ${{ matrix.os }}
 
     steps:
       - uses: actions/checkout@v2
 
+      - name: install system deps
+        if: contains(matrix.os, 'ubuntu')
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libgtk-3-dev libxdo-dev libayatana-appindicator3-dev
+
       - name: install stable
         uses: actions-rs/toolchain@v1
         with: