Add Sphinx docs

[ewu63]

Purpose

Partially addresses #14.

Expected time until merged

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

[codecov]

Codecov Report

Merging #55 (fecfdc8) into main (63ba8eb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #55   +/-   ##
=======================================
  Coverage   21.25%   21.25%           
=======================================
  Files           3        3           
  Lines        2329     2329           
=======================================
  Hits          495      495           
  Misses       1834     1834           

Impacted Files	Coverage Δ
cgnsutilities/cgnsutilities.py	26.96% <ø> (ø)

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[ewu63]

The docs are working now.

[sseraj]

Could you add the badge to the README?