Made a dockerfile which utilizes caching of npm

Dockerfile

@@ -16,19 +16,21 @@ RUN mkdir -p /usr/src && \
   make install) && \
  rm -rf /usr/src/{bcm2835-1.60,pigpio}
 
-WORKDIR /iot-project
-
-COPY . /iot-project
-
-# Build server
 WORKDIR /iot-project/server
+
+COPY ./server/package*.json ./
 RUN npm install
+COPY ./server ./
 RUN npm run clean
 RUN npm run build
 
+
+
 # Build client
 WORKDIR /iot-project/client
+COPY ./client/package*.json ./
 RUN npm install
+COPY ./client ./
 RUN npm run build:prod
 
 EXPOSE 8080