Improve README.md
This merge request improves the README file:
- It updates the help messages produced by
bin/dico -h
- It adds subtitle and purpose for the subcommand
kernel
- It adds the help message produced by
bin/dico kernel -h
and an example. - It adds subtitle and purpose for subcommand
condense
- It adds subcommand
convert
and example in README.md
Edited by Medina Cardenas, Lorena Giovanna