Add a renderable that transforms text in "child" renderables, add transform-specific versions

[davep]

Type of changes

• [ ] Bug fix
• [X] New feature
• [ ] Documentation / docstrings
• [ ] Tests
• [ ] Other

Checklist

• [X] I've run the latest black with default args on new code.
• [X] I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• [X] I've added tests for new code.
• [X] I accept that @willmcgugan may be pedantic in the code review.

Description

This adds a renderable called text_transform.TextTransform that can be used to apply a given text transformation to a given renderable, and which can also serve as a base class for other text transformations. This also adds child classes of this that upper-case, lower-case and swap-case text.

Examples:

>>> console.print( TextTransform( "Hello, World!", str.upper ) )
HELLO, WORLD!
>>> console.print( Upper( "Hello, World!" ) )
HELLO, WORLD!
>>> console.print( Lower( "Hello, World!" ) )
hello, world!
>>> console.print( SwapCase( "Hello, World!" ) )
hELLO, wORLD!

[codecov-commenter]

Codecov Report

Merging #2448 (7a80998) into master (19e518f) will decrease coverage by 3.02%. The diff coverage is 98.57%.

@@            Coverage Diff             @@
##           master    #2448      +/-   ##
==========================================
- Coverage   98.71%   95.68%   -3.03%     
==========================================
  Files          73       73              
  Lines        7771     7786      +15     
==========================================
- Hits         7671     7450     -221     
- Misses        100      336     +236     

Flag	Coverage Δ
unittests	95.68% <98.57%> (-3.03%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
rich/default_styles.py	100.00% <ø> (ø)
rich/logging.py	100.00% <ø> (ø)
rich/progress.py	92.76% <ø> (ø)
rich/segment.py	98.72% <93.10%> (+<0.01%)	:arrow_up:
rich/_inspect.py	100.00% <100.00%> (ø)
rich/box.py	100.00% <100.00%> (ø)
rich/cells.py	96.05% <100.00%> (-3.95%)	:arrow_down:
rich/color.py	100.00% <100.00%> (ø)
rich/console.py	96.71% <100.00%> (-1.58%)	:arrow_down:
rich/highlighter.py	100.00% <100.00%> (ø)
... and 8 more

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[willmcgugan]

Looks good to me. 👍