Add docker example

Help users with docker deployment

docs/content/2.guide/5.deploy/3.docker.md

@@ -0,0 +1,42 @@
+# Deployment Docker
+
+## Dockerfile
+
+```Dockerfile
+FROM node:17-alpine
+
+RUN mkdir -p /usr/src/nuxt3-app
+WORKDIR /usr/src/nuxt3-app
+COPY package.json /usr/src/nuxt3-app/package.json
+COPY . .
+
+## When packaging on docker
+# RUN npm install pnpm -g
+# RUN pnpm i --shamefully-hoist
+# RUN pnpm run build
+
+EXPOSE 3000 
+
+ENTRYPOINT ["node", ".output/server/index.mjs"]
+```
+
+## docker-compose
+
+```ts
+version: '3.7'
+
+services:
+  nuxt3_app:
+    container_name: nuxt3_app
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: nuxt3_app:0.0.2
+    volumes:
+      - '.:/nuxt3-app'
+      - '/nuxt3-app/node_modules'
+    ports:
+      - 3000:3000
+    environment:
+      - CHOKIDAR_USEPOLLING=true
+```