Add workflow (sans the deployment)

Ref: https://vitepress.dev/reference/cli

.github/workflows/docs-deploy.yml

@@ -0,0 +1,35 @@
+name: "Deploy (docs)"
+
+on:
+    # Run on every push to main that changes docs/
+    push:
+        branches: [main]
+        paths:
+            - "docs/**"
+            - ".github/workflows/web-lint.yml"
+    # Also allow manually running the action
+    workflow_dispatch:
+
+jobs:
+    deploy:
+        runs-on: ubuntu-latest
+        defaults:
+            run:
+                working-directory: docs
+        steps:
+            - name: Checkout code
+              uses: actions/checkout@v4
+
+            - name: Setup node and enable yarn caching
+              uses: actions/setup-node@v4
+              with:
+                  node-version: 20
+                  cache: "yarn"
+                  cache-dependency-path: "docs/yarn.lock"
+
+            - name: Install dependencies
+              run: yarn install
+
+            - name: Build production site
+              # Will create docs/.vitepress/dist
+              run: yarn build