Add more context to README
Resolve todo on supporting multiple platforms
Add `htop` package
Add `oh-my-zsh` installation script

This probably needs some work because of the GUI interactions in the
script.

Use the manual way:
https://github.com/robbyrussell/oh-my-zsh#the-manual-way
Improve ubuntu support

repos get only registered once.
Add warning to README file
Introduce more tasks