chore(docs): add feedback loop and code re-use to Why Nexus

[Nayni]

As mentioned in #585

These are some of the benefits that I mentioned.

I think most of the gist of the initial issue is now in the docs. I extended the section with what I personally think are two of the major benefits of going to a Code first approach and especially using Nexus:

• The instant feedback loop
• The reduce repetitive work

The one thing which I think still deserves a highlight is the "endless" possibilities with plugins. I tried to hint at it in the context of repetitive work but in fact plugins can do way more. But I wasn't sure on how to fit it in or word it properly.

[codecov]

Codecov Report

Merging #725 (993051c) into develop (fa3fd96) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #725   +/-   ##
========================================
  Coverage    93.62%   93.62%           
========================================
  Files           46       46           
  Lines         2932     2932           
  Branches       692      692           
========================================
  Hits          2745     2745           
  Misses         185      185           
  Partials         2        2           

[jasonkuhrt]

ty!