Add a slide on `numeric_limits`

[bernhardmgruber]

This was a question during the 4th HEP C++ course, how to get the smallest and largest value for a fundamental type.

[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. Please manually close it, if it is no longer relevant, or ask for help or support to help getting it unstuck. Let me bring this to the attention of @klieret @wdconinc @michmx for now.