Ensure the Knative Community tab is hosted in the old Hugo format

[omerbensaadon]

Description:

Since we want to limit the scope of our work in this first release of the MkDocs site, we have opted to keep our Community tab in the existing Hugo template and wire it together with the MkDocs prototype.

See: https://knative.dev/blog/

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Story

As Danny the Developer
I want to check out the Knative Community Tab  
So that I can find information on the Knative Community

Acceptance Criteria

Community Tab Present

GIVEN I am on the new MkDocs site
WHEN I look at the main site navigation tabs  
THEN I see a tab named "Community" 

MkDocs -> Hugo

GIVEN I am on the new MkDocs site 
WHEN I click on "Community" in the main site navigation tabs 
THEN I am brought to the Knative Community site (currently knative.dev/community) hosted in Hugo

Hugo -> MkDocs

GIVEN I am on the Knative Community site hosted in Hugo 
WHEN I click on "Documentation" in the header
THEN I am brought back to the homepage in the MkDocs site

Known Issues and Considerations:

• This issue does not cover broken links and will be accepted nearly broken. We'll do clean-up in a different issue.

[omerbensaadon]

Closed by #3558