docs: Add RELEASE.md documentation

[jonathan-innis]

Fixes #841

Description

This change adds the RELEASE.md file as called-out by the migration requirements for the K8s template project here: kubernetes/org#4562 (comment).

How was this change tested?

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jonathan-innis

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[coveralls]

Pull Request Test Coverage Report for Build 7225994635

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.07%) to 79.891%

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Files with Coverage Reduction	New Missed Lines	%
pkg/controllers/provisioning/scheduling/nodeclaim.go	2	88.17%
pkg/test/expectations/expectations.go	2	95.01%
pkg/controllers/provisioning/scheduling/preferences.go	7	86.67%

Totals
Change from base Build 7219395548:	-0.07%
Covered Lines:	7648
Relevant Lines:	9573

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💛 - Coveralls

[jmdeal]

/lgtm