Add basic CI configuration (#3)

This commit adds a basic initial CI configuration. This just adds a
single job that tests a build, runs `cargo fmt` and `cargo clippy` to
ensure consistent formatting and style, and then runs the unittests.
This provides coverage of the repo basics and we can expand and tweak
this over time as the library evolves.

.github/workflows/main.yml

@@ -0,0 +1,27 @@
+---
+name: Rust
+
+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: Rust Format
+      run: cargo fmt --all -- --check
+    - name: Build
+      run: cargo build --verbose
+    - name: Clippy
+      run: cargo clippy -- -D warnings
+    - name: Run tests
+      run: cargo test --verbose