.github: Add release notes block to pull request template
.github: Add release notes block to pull request template

Signed-off-by: Stephen Augustus <f96984fef9637085f0559f1484dfd4e99545cd6e@vmware.com>

ericchiang/dex,ericchiang/dex,ericchiang/dex,coreos/dex,coreos/dex,coreos/dex