doc: better usage example
doc: better usage example

provide an example with a LGTM

PR-URL: https://github.com/joyent/git-apply-pr/pull/7
Reviewed-By: Julien Gilli <498f087c128f7ba877a9c41cd8ff0767d4a0d56c@fastmail.fm>

robertkowalski/git-apply-pr,joyent/git-apply-pr