Day 1 afternoon: include explanation about `cat`
In the notebook about unix shell there is no explanation of how to use cat
to view the content of a file.
This command is used only once in the advanced topics sections, however it is a simple command that can be helpful to use.
I propose to add a sentence mentioning it such as: If one wants to check the content of a file within the CLI, one can do cat draft.txt
.