Add basic GH workflow for dapp workspace

This is an initial implementation of the CI process to check formatting
in `dapp` workspace.

.github/workflows/dapp.yaml

@@ -0,0 +1,32 @@
+name: dApp
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - "dapp/**"
+  pull_request:
+
+defaults:
+  run:
+    working-directory: ./dapp
+
+jobs:
+  dapp-format:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: "dapp/.nvmrc"
+          cache: "yarn"
+          cache-dependency-path: "dapp/yarn.lock"
+
+      - name: Install Dependencies
+        run: yarn install --prefer-offline --frozen-lockfile
+
+      - name: Format
+        run: yarn format