fix docs theme with latest mkdocs-material & pin docs dev environment

[M00nF1sh]

description

1. fix docs theme with latest mkdocs-material. (the latest v7.1.5 mkdocs-material have changes breaking current docs).
2. pin docs dev environment by
   1. add pipenv for docs dependencies.
   2. add makefile targets for preview

usage

1. Install pipenv. either by (python3 -m pip install pipenv or brew install pipenv)
2. run make docs-preview to preview docs
3. run make docs-publish to publish docs

[codecov-commenter]

Codecov Report

Merging #2023 (35ec0b8) into main (07a29df) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2023   +/-   ##
=======================================
  Coverage   49.24%   49.24%           
=======================================
  Files         130      130           
  Lines        7034     7034           
=======================================
  Hits         3464     3464           
  Misses       3292     3292           
  Partials      278      278           

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kishorj, M00nF1sh

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• OWNERS [M00nF1sh,kishorj]

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[kishorj]

/lgtm