Doc updates for customization and installation.

[jolheiser]

Resolves #6172

I think the docs could use more cleanup, but I figured this would be a good start.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@1cf3fc3). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #6176   +/-   ##
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  Coverage          ?   38.87%           
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  Files             ?      354           
  Lines             ?    50210           
  Branches          ?        0           
=========================================
  Hits              ?    19517           
  Misses            ?    27867           
  Partials          ?     2826

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[zeripath]

Thanks for doing this. It's really helpful to update these docs. I think people have genuinely struggled to get things to work and if we can at all help reduce that we should.

[techknowlogick]

Thanks for updating the documentation. It is really appreciated. I'm still a bit jetlagged so I'm going to take a step back from reviewing any more PRs tonight, so I will let others give their 👍