Update Dockerfile

Dockerfile

@@ -1 +1,19 @@
+#Use the official Node.js image.
 FROM node
+# Set the working directory.
+WORKDIR /usr/src/app
+
+# Copy package.json and package-lock.json.
+COPY package*.json ./
+
+# Install dependencies.
+RUN npm install express body-parser
+
+# Copy the rest of the application code.
+COPY . .
+
+# Expose the port the app runs on.
+EXPOSE 3000
+
+# Command to run the app.
+CMD ["node", "app.js"]