It's come up several times that it'd be nice to have somewhere to dump
drgn scripts that people write while debugging without requiring them to
be cleaned up and scrutinized in code review. Serapheim Dimitropoulos
noted that several projects have a "contrib" directory for this purpose.
See [1]. Let's create one, document it, exclude it from pre-commit, and
move our (mostly unmaintained) examples there.
1: https://drewdevault.com/2020/06/06/Add-a-contrib-directory.html
Signed-off-by: Omar Sandoval <osandov@osandov.com>