update app with docker files

Dockerfile

@@ -0,0 +1,21 @@
+## base image
+FROM node:13.12.0-buster-slim
+
+## set working directory
+WORKDIR /usr/src/app
+
+## add `/usr/src/app/node_modules/.bin` to $PATH
+ENV PATH /usr/src/app/node_modules/.bin:$PATH
+
+## install and cache app dependencies
+COPY package.json /usr/src/app/package.json
+
+## create user "node" and give permissions
+RUN chown -R node:node . && chmod -R 755 .
+USER node
+
+# install app dependencies
+RUN npm install
+
+## start app
+CMD ["npm", "start"]