gitlint: allow commit messages to contain long footnotes

[phlogistonjohn]

Configure gitlint to ignore lines that start like [1]: or [2] such that we can have long text like URLs in the commits without triggering other gitlint body rules.

PR contains two test commits to demonstrate the change that must be removed prior to merging.

[phlogistonjohn]

This PR also enables the extremely useful feature of being able to put ascsii art in the message without tickling gitlint. Just prefix each line with [0] or something and go to town, like so:

stuff: useful things

This is an important commit message.

[0]  ___________________
[0] < this commit rocks >
[0]  ------------------- 
[0]    \
[0]     \
[0]         .--.
[0]        |o_o |
[0]        |:_/ |
[0]       //   \ \
[0]      (|     | )
[0]     /'\_   _/`\
[0]     \___)=(___/
[0]    
[0]                           PS. Please don't actually do this [1].
[0]
[0]
[1]                                      Unless your ascii art is actually a diagram or something