* add support for autolabel stale PR
automatically labels stale PRs
* stale label is kind/stale
updates the stale label to reflect
existing project labels
* adds a relevant stale message
for both PRs and issues there is now a more
descriptive and relevant message
when the action marks something stale
* no auto-close on stale issues/prs
uses the exempt flag to ignore issues already marked
stale. this will allow us to auto label stale,
and then ignore them so they do not get auto
closed.
