chore: updated frontend and backend Node.JS version to 16 (LTS)

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:15
+FROM node:16
 
 RUN npm install -g nodemon
 

frontend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:14
+FROM node:16
 
 RUN apt-get update
 RUN apt-get install nginx -y