Add CI github action

Author: MalcolmMielle

.github/workflow/ci.yml

@@ -0,0 +1,35 @@
+# This is a basic workflow to help you get started with Actions
+name: CI
+
+# Controls when the workflow will run
+on:
+  # Triggers the workflow on push or pull request events but only for the main branch
+  push:
+    branches: [main]
+    paths-ignore:
+      - '**/README.md'
+  pull_request:
+    branches: [main]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+jobs:
+  test:
+    name: Test on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v2
+        with:
+          distribution: 'zulu'
+          java-version: '11'
+      - uses: subosito/flutter-action@v1
+        with:
+          channel: 'stable'
+      - run: dart --version
+      - run: flutter --version
+      - run: flutter analyze

README.md

@@ -1,5 +1,6 @@
 ## Libadwaita ❤️ Flutter
 
+![CI](https://github.com/gtk-flutter/libadwaita/actions/workflows/ci.yml/badge.svg)
 [![Pub.dev](https://img.shields.io/pub/v/libadwaita.svg)](https://pub.dev/packages/libadwaita)
 [![License](https://img.shields.io/github/license/gtk-flutter/libadwaita?color=indigo)](LICENSE)
 [![Maintainer](https://img.shields.io/badge/Maintainer-prateekmedia-informational)](https://github.com/prateekmedia)