build: add ci

.github/tests.yaml

@@ -0,0 +1,21 @@
+name: Tests
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: aiken-lang/[email protected]
+        with:
+          version: v1.0.21-alpha
+
+      - run: aiken fmt --check
+      - run: aiken check
+      - run: aiken build