Update to instructions

[ndunn219]

Just a couple helpful updates to the instructions:

1. Add pip install autopep8 if you don't have it installed.
2. run npm i && npm run lint --fix from the frontend directory.

[zessx]

Plus, the npm commands may fail because we'll run it on our local machine (therefore having various Node versions).
For example, it is failing with Node 15, I had to load Node 10 with nvm to make it work.

I have the feeling these commands should be ran inside a Docker image, but instructions are confusing.

[zessx]

@vchaptsev Shouldn't it be this instead:

docker-compose up --build
docker-compose run backend autopep8 -r --in-place --aggressive .
docker-compose run frontend npm i && npm run lint --fix