ios: First attempt at CI

.github/workflows/ci.yml

@@ -0,0 +1,18 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: subosito/flutter-action@v1
+        with:
+          flutter-version: "1.20.2"
+      - run: flutter pub get
+      - run: flutter test
+      - run: flutter build ios --release --no-codesign