Add basic workflow

.github/workflows/ci.yaml

@@ -0,0 +1,34 @@
+name: Openmina CI
+on: [ push, pull_request, workflow_dispatch ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Git checkout
+        uses: actions/checkout@v3
+
+      - name: Setup Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+          components: rustfmt, clippy
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+
+      - name: Clippy
+        uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+        # don't fail the job until clippy is fixed
+        continue-on-error: true
+
+      - name: Release build
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --release --bin openmina