feat(docs): add toggle for light/dark mode support

[moshevayner]

What this PR does / why we need it:
This adds a long-overdue toggle for dark mode support in our docs website. The website will automatically align with the OS theme (light/dark), but it's possible to toggle dark mode on/off by using the switch.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):

Special notes for your reviewer:
Followed mkdocs insturctions here

Netlify Preview deploy here

And also screenshots below.

Light Mode Screenshot (Same as before):

Dark Mode Screenshot:

[rifelpet]

Very cool! Looking at the docs I see we can add a media selector to default to the operating system's light/dark preference:

https://squidfunk.github.io/mkdocs-material/setup/changing-the-colors/#automatic-light-dark-mode

Any chance you can add that here as well?

[moshevayner]

Very cool! Looking at the docs I see we can add a media selector to default to the operating system's light/dark preference:

https://squidfunk.github.io/mkdocs-material/setup/changing-the-colors/#automatic-light-dark-mode

Any chance you can add that here as well?

Sure thing!
That's a great catch. Thanks for finding that!

UPDATE: DONE!

[moshevayner]

/retest

[moshevayner]

/retest

[hakman]

Thanks @moshevayner! :smiling
/lgtm
/assign @rifelpet

[k8s-ci-robot]

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