releng: Add GitHub issue template for Release Manager onboarding
releng: Add GitHub issue template for Release Manager onboarding

This template includes multiple punchlists detailing the access
required for a new Release Manager, including updates to:
- documentation
- GitHub teams
- Google Groups
- OWNERS/OWNERS_ALIASES in multiple repos
- Slack User Groups

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

kubernetes/sig-release