Add crates.io publish workflow on GitHub release

Triggers on release publish events and runs cargo publish with
the CARGO_REGISTRY_TOKEN secret.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: lightsofapollo

.github/workflows/publish.yml

@@ -0,0 +1,19 @@
+name: Publish to crates.io
+
+on:
+  release:
+    types: [published]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo publish
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}