docs: move usage to quickstart

[tabathad]

Moves the usage page under the Quick Start section. The current usage page is really about kicking-off rather than a proper deployment guide, so it fits better in the quickstart section.

Discussed in meeting: #1397

[netlify]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.78%. Comparing base (3392dd0) to head (097d2ff).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1417   +/-   ##
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  Coverage   81.78%   81.78%           
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  Files          67       67           
  Lines        4766     4766           
  Branches      827      827           
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  Hits         3898     3898           
  Misses        852      852           
  Partials       16       16           

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[kriswest]

Thank you for doing this - installation appears to be an orphan in the nav, can we move that into quickstart also?

[kriswest]

LGTM