👌 Auto-generate `needs` JSON schema

[chrisjsewell]

(currently based on top of #1129)

description to come ...

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.30409% with 20 lines in your changes missing coverage. Please review.

Project coverage is 85.76%. Comparing base (cf5598f) to head (ae08f35). Report is 35 commits behind head on master.

Files	Patch %	Lines
sphinx_needs/needsfile.py	21.05%	15 Missing :warning:
sphinx_needs/directives/needflow.py	77.77%	2 Missing :warning:
sphinx_needs/api/need.py	66.66%	1 Missing :warning:
sphinx_needs/config.py	96.96%	1 Missing :warning:
sphinx_needs/data.py	98.52%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1132      +/-   ##
==========================================
- Coverage   85.90%   85.76%   -0.14%     
==========================================
  Files          56       56              
  Lines        6511     6560      +49     
==========================================
+ Hits         5593     5626      +33     
- Misses        918      934      +16     

Flag	Coverage Δ
pytests	85.76% <88.30%> (-0.14%)	:arrow_down:

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[chrisjsewell]

superceded by #1230