Create CAPG book from existing docs

[salasberryfin]

/kind feature

What this PR does / why we need it:

This PR consolidates the existing documentation into a first version of the CAPG book.

Once this initial version is published, we can iterate over the contents and improve the user/developer experience.

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 #490

Special notes for your reviewer:

This PR is still WIP until #1131 is approved and merged.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Publish CAPG book

[k8s-ci-robot]

Hi @salasberryfin. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[richardcase]

/ok-to-test

[richardcase]

@salasberryfin now #1131 has merged can this be moved from wip?

[salasberryfin]

I was hoping that we could have the netlify site before, but it's not blocking us from having this reviewed and merged.

[richardcase]

Thanks @salasberryfin

/approve

[cpanato]

/lgtm
/approve

thanks

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, richardcase, salasberryfin

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