react-express-mongodb: rename server to backend

The goal here is to keep the same structure than the other examples.
Also, considering that it has a "frontend" folder, the equivalent for
the server should be "backend".

Signed-off-by: Jérémie Drouet <jeremie.drouet@gmail.com>

react-express-mongodb/backend/Dockerfile

@@ -0,0 +1,27 @@
+FROM node:13.13.0-stretch-slim
+
+#Argument that is passed from docer-compose.yaml file
+ARG NODE_PORT
+
+#Echo the argument to check passed argument loaded here correctly
+RUN echo "Argument port is : $NODE_PORT"
+
+# Create app directory
+WORKDIR /usr/src/app
+
+#COPY . .
+COPY . .
+
+# Install app dependencies
+# A wildcard is used to ensure both package.json AND package-lock.json are copied
+# where available (npm@5+)
+RUN npm install
+
+
+#In my case my app binds to port NODE_PORT so you'll use the EXPOSE instruction to have it mapped by the docker daemon:
+
+EXPOSE ${NODE_PORT}
+
+CMD npm run dev
+
+