chore(ci): Check formatting

Uses the same check / action as in `smawk`.

.github/workflows/build.yml

@@ -270,3 +270,21 @@ jobs:
       - name: Deploy textwrap-wasm-demo-app
         if: steps.git-add.outputs.has-changes == 'true'
         run: git push origin
+
+  format:
+    name: Format
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      # We use an unstable rustfmt feature and we thus need the
+      # nightly channel to enforce the formatting.
+      - name: Setup Rust nightly
+        run: rustup default nightly
+
+      - name: Install rustfmt
+        run: rustup component add rustfmt
+
+      - name: Check Formatting
+        uses: dprint/[email protected]

dprint.json

@@ -0,0 +1,19 @@
+{
+  "markdown": {
+    "textWrap": "always"
+  },
+  "exec": {
+    "commands": [{
+      "command": "rustfmt",
+      "exts": ["rs"]
+    }]
+  },
+  "excludes": ["target/"],
+  "plugins": [
+    "https://plugins.dprint.dev/json-0.17.4.wasm",
+    "https://plugins.dprint.dev/markdown-0.16.1.wasm",
+    "https://plugins.dprint.dev/toml-0.5.4.wasm",
+    "https://plugins.dprint.dev/exec-0.4.3.json@42343548b8022c99b1d750be6b894fe6b6c7ee25f72ae9f9082226dd2e515072",
+    "https://plugins.dprint.dev/prettier-0.27.0.json@3557a62b4507c55a47d8cde0683195b14d13c41dda66d0f0b0e111aed107e2fe"
+  ]
+}