ci: basic GA for unit tests on various platforms

.github/workflows/main.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on: [pull_request]
+
+jobs:
+  linter:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+            toolchain: stable
+            components: rustfmt
+            override: true
+      - name: rustfmt
+        run: cargo fmt -- --check
+
+  unit_tests:
+    needs: linter
+    strategy:
+      matrix:
+        toolchain:
+          - 1.48
+          - nightly
+        os:
+          - ubuntu-latest
+          - macOS-latest
+          - windows-latest
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Checkout source code
+        uses: actions/checkout@v2
+      - name: Install Rust ${{ matrix.toolchain }} toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ matrix.toolchain }}
+          override: true
+          profile: minimal
+      - name: Test on Rust ${{ matrix.toolchain }}
+        run: cargo test --verbose