Try to get a builder going.

.github/workflows/builder.yml

@@ -0,0 +1,26 @@
+name: Matrix
+on:
+  - pull_request
+  - push
+jobs:
+  main:
+    strategy:
+      matrix:
+        rust:
+          - stable
+          - beta
+          - nightly
+    name: ${{matrix.rust}}
+    runs-on: x86_64-linux
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@v1
+        with:
+          toolchain: ${{matrix.rust}}
+          components: rustfmt, clippy
+      - run: rustup --version
+      - run: rustc -vV
+
+      - run: cargo clippy -- --deny clippy::pedantic
+      - run: cargo fmt --all -- --check
+      - run: cargo test