Document `chimera-prunekernels`

[triallax]

we get asked about this quite often on irc

[sidkshatriya]

For now we can simply say that it is a shell script and curious people can inspect it:

$EDITOR /bin/chimera-prunekernels

[nekopsykose]

writing documentation that says 'this program is a shell script, look at it yourself' is not particularly friendly or useful to whoever is reading the documentation, it's the same as just not having any docs at all

[triallax]

i agree, i was thinking about actually explaining what the script does and showing some example usages