feat: add support for Kubernetes 1.18.12

[mboersma]

Reason for Change:

See https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.18.md#changelog-since-v11811

Issue Fixed:

Credit Where Due:

Does this change contain code from or inspired by another project?

• No
• Yes

Requirements:

• Kubernetes artifacts built and pushed by Azure Pipelines
• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #4043 (c0d3856) into master (5dbff4c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4043   +/-   ##
=======================================
  Coverage   73.08%   73.08%           
=======================================
  Files         145      145           
  Lines       21776    21776           
=======================================
  Hits        15914    15914           
  Misses       4829     4829           
  Partials     1033     1033           

Impacted Files	Coverage Δ
pkg/api/common/versions.go	96.37% <ø> (ø)

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[jackfrancis]

Thanks for adding this bit of comment accounting!

[jackfrancis]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis, mboersma

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