Add CI workflow

.github/workflows/main.yml

@@ -0,0 +1,24 @@
+name: Build
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Build
+      run: cargo build
+    - name: Build no_std
+      run: cargo build --no-default-features
+    - name: Build no_std with allocator
+      run: cargo build --no-default-features --features alloc
+    - name: Run tests
+      run: cargo test