Allow [skip ci] tag to be upper case

[nullobject]

It seems that the [skip ci] tag must be specified in lower case. It would be better if it was case-insensitive so that users can match their preferred tagging style (we use upper case for example).

[keithpitt]

A fix for this is going live now :) In about 10 minutes, both [skip ci] and [SKiP cI]` will #justwork!

[nullobject]

Ace, thanks very much 🎉