instancetype: Separate docs and give ownership to sub-project

[lyarwood]

/cc @aburdenthehand
/cc @0xFelix
/cc @vladikr

What this PR does / why we need it:

I'd like to rework the instance type docs quite extensively during the 1.4 cycle. Ahead of this it would be useful if we could give ownership of the docs to the instance type sub-project approvers as has already happened with the code within KubeVirt itself.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #818

Special notes for your reviewer:

Checklist

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• Design: A design document was considered and is present (link) or not required
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• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
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Release note:

NONE

[kubevirt-bot]

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[0xFelix]

Good idea!

/lgtm

[0xFelix]

@phoracek PTAL, thanks!

[phoracek]

@lyarwood I fully support and appreciate you owning your part of the user-guide. However, would you please split the part where you introduce a new subsection of "User Workloads" page from the OWNERS change? It may require you to explicitly list all the files your group owns instead of having a convenient subdirectory.

I would like @aburdenthehand to review the change to the structure, and that may take a while. Personally, I don't like that it adds another layer to the menu, but perhaps we can make it work.

[kubevirt-bot]

PR needs rebase.

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