allow rich cast to return rich cast

[willmcgugan]

Fixes #2083

[codecov-commenter]

Codecov Report

Merging #2089 (e23b0bb) into master (91e0146) will decrease coverage by 0.02%.
The diff coverage is 92.06%.

@@            Coverage Diff             @@
##           master    #2089      +/-   ##
==========================================
- Coverage   99.49%   99.46%   -0.03%     
==========================================
  Files          73       72       -1     
  Lines        7361     7333      -28     
==========================================
- Hits         7324     7294      -30     
- Misses         37       39       +2     

Flag	Coverage Δ
unittests	99.46% <92.06%> (-0.03%)	⬇️

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Impacted Files	Coverage Δ
rich/__init__.py	100.00% <ø> (ø)
rich/align.py	100.00% <ø> (ø)
rich/highlighter.py	100.00% <ø> (ø)
rich/layout.py	100.00% <ø> (ø)
rich/table.py	100.00% <ø> (ø)
rich/console.py	99.14% <82.14%> (-0.49%)	⬇️
rich/_win32_console.py	91.48% <100.00%> (+1.48%)	⬆️
rich/_windows_renderer.py	100.00% <100.00%> (ø)
rich/ansi.py	100.00% <100.00%> (ø)
rich/cells.py	100.00% <100.00%> (ø)
... and 7 more

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