Update windows setup instructions

[Ariana-B]

Reason for this pull request

Windows developer setup instructions are out of date and incomplete.

Proposed changes

• Update windows setup guide to be more complete

• Closes #xxxx

• Tests added / passed

• Fully documented, including docs/about/whats_new.rst for all changes

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📚 Documentation preview 📚: https://datacube-core--1526.org.readthedocs.build/en/1526/

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (9fb8c8c) 91.75% compared to head (f393c36) 91.79%.
Report is 5 commits behind head on develop.

Files	Patch %	Lines
datacube/index/memory/_datasets.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1526      +/-   ##
===========================================
+ Coverage    91.75%   91.79%   +0.04%     
===========================================
  Files          132      132              
  Lines        14552    14624      +72     
===========================================
+ Hits         13352    13424      +72     
  Misses        1200     1200              

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[SpacemanPaul]

I don't think we should be telling them to git clone or run the integration tests here.

Just tell them the bare minimum they need to get a conda environment working on windows - with datacube coming from PIP or Condaforge.