Add an example about doing a or b context matching

[fidgetingbits]

Talon doesn't directly support or for context matching, so if you want a context to match something like tag: foo OR win.title: bar but not both, you have to do something like:

tag: foo
and not win.title: bar

win.title: bar
and not tag: foo

If you want it to match on one or the other, or both, then you have to do like:

tag: foo
and not win.title: bar

win.title: bar
and not tag: foo

tag: foo
win.title: bar

Pretty sure this isn't documented anywhere except in the 3 month slack hole.