Makefile: fix major and major-minor docker release tags

[joelanford]

Description of the change:

• Updates release documentation to provide explicit commands to run to create appropriate tag.
• Updates the Makefile to be more resilient to non-annotated tags.

Motivation for the change:
When we pushed the v1.18.1 tag, the v1 and v1.18 image tags were not pushed as expected. It seems like this happened because:

1. v1.18.1 was not an annotated tag.
2. The Makefile's use of a git describe command to check the tag of HEAD assumed only annotated tags.

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /docs
• Commit messages sensible and descriptive

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: joelanford

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• OWNERS [joelanford]

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[codecov]

Codecov Report

Merging #801 (8eb37f1) into master (37551d4) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #801      +/-   ##
==========================================
+ Coverage   51.18%   51.20%   +0.01%     
==========================================
  Files         103      103              
  Lines        9078     9077       -1     
==========================================
+ Hits         4647     4648       +1     
+ Misses       3551     3550       -1     
+ Partials      880      879       -1     

Impacted Files	Coverage Δ
alpha/action/render.go	63.87% <0.00%> (+0.85%)	⬆️

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[kevinrizza]

/lgtm