update for python3 and run with 0.0.0.0

[johnfelipe]

root@felipe:~/whatsapp-web-reveng# docker run -p 2019:2019 -p 2018:2018 whatsapp-web-reveng:latest

> whatsapp-web-reveng@1.0.0 __run_in_docker
> concurrently "node index.js" "python backend/whatsapp_web_backend.py"

[1] /bin/sh: 1: python: not found
[1] python backend/whatsapp_web_backend.py exited with code 127
[0] whatsapp-web-reveng API server listening on port 2019
[0] whatsapp-web-reveng HTTP server listening on port 2018

i change for build

RUN apt-get update && apt-get install -y \
    python3-pip