Add dockerfile and docker documentation in README.md

Dockerfile

@@ -0,0 +1,30 @@
+# docker build . -t mokuappio/serverless-invoices
+# docker run -p 80:8080 -d mokuappio/serverless-invoices
+
+FROM node:16
+
+RUN npm install -g http-server
+
+# Create app directory
+WORKDIR /app
+
+# Copy package.json and package-lock.json
+COPY package*.json ./
+
+# Install
+RUN npm install
+
+# Bundle app source
+COPY . .
+
+# Copy config (grrrr not written in README!! https://github.com/mokuappio/serverless-invoices/issues/9)
+COPY src/config/app.config.example.js ./src/config/app.config.js
+
+# Build the app
+RUN npm run build
+
+# Choose what port to expose
+EXPOSE 8080
+
+# Run the app
+CMD ["http-server", "dist"]