Make the README restructured text

[jdavies-st]

Resolves #5643 / JP-1865

Description

This PR converts the README from markdown format to restructured text format. This allows it to be broken up into pieces and the general information to be included in the long_description which forms the landing page on PyPI and the installation in our docs, and the readme in the repo here having extended information for internal STScI usage, such as DMS builds, SDP installaions, etc.

Checklist

• [x] Tests
• [x] Documentation
• [ ] Change log
• [x] Milestone
• [x] Label(s)

[codecov[bot]]

Codecov Report

Merging #6058 (9993492) into master (fda15ac) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6058   +/-   ##
=======================================
  Coverage   77.12%   77.12%           
=======================================
  Files         402      402           
  Lines       34325    34325           
=======================================
  Hits        26474    26474           
  Misses       7851     7851           

Flag	Coverage Δ		*Carryforward flag
nightly	77.13% <ø> (ø)		Carriedforward from fda15ac
unit	55.17% <ø> (ø)

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[hbushouse]

@nden @stscieisenhamer is this still a good thing to have (README in rst format) in order to facilitate info on pypi? If so, it'll obviously need a lot of rebasing to bring it up to date before merging.

[stscieisenhamer]

Unfamiliar with the pypi advantages, but this seems like a reasonable thing to do. Presume github handles both when it displays.

[jdavies-st]

Closing this as it is very out-of-date and not needed anymore.