Add Windows CI

Author: jchyb

.github/workflows/CI.yml

@@ -6,11 +6,14 @@ on:
       - master
 jobs:
   test-all:
-    runs-on: ubuntu-18.04
-      steps:
-        - uses: actions/checkout@v2
-        - uses: olafurpg/setup-scala@v13
-        - name: Unit tests
-          run: sbt cli/test
-        - name: Intergration tests
-          run: sbt cliIntegration/scripted
+    runs-on: ${{matrix.OS}}
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, windows-2019]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: olafurpg/setup-scala@v13
+      - name: Unit tests
+        run: sbt cli/test
+      - name: Intergration tests
+        run: sbt cliIntegration/scripted