Added Docker + enhanced README design

[ilolm]

1. Created docker image.
2. Enhanced ReadMe design.
3. Added docker to ReadMe.

Also you have to build this image and push it to docker hub and give it this name p-society/typeracer-cli:latest

Steps you need to do:

cd docker/
sudo docker image build -t p-society/typeracer-cli:latest .
sudo docker login
sudo docker image push p-society/typeracer-cli:latest