Add a Dockerfile for the React App

## Description

Dockerize the React App. You can specify a `Dockerfile` in the `client` directory, and add the following:

```
FROM node:latest as build
WORKDIR /usr/src/app
COPY package.json /usr/src/app
RUN npm install
COPY . /usr/src/app
CMD [ "npm" , "start" ]
```

Make sure to validate it on your own local machine that the Dockerfile works before pushing changes.