feat: add prefix/suffix options for boolean, number and string widgets

[KaneFreeman]

Inspired by decaporg/decap-cms#6836

Resolves #887

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[codecov]

Codecov Report

Merging #888 (8a87e44) into next (4a908d5) will increase coverage by 0.11%.
Report is 1 commits behind head on next.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             next     #888      +/-   ##
==========================================
+ Coverage   52.30%   52.42%   +0.11%     
==========================================
  Files         232      232              
  Lines        9917     9942      +25     
  Branches     2593     2612      +19     
==========================================
+ Hits         5187     5212      +25     
  Misses       4347     4347              
  Partials      383      383              

Files Changed	Coverage Δ
...ckages/core/src/widgets/boolean/BooleanControl.tsx	100.00% <100.00%> (ø)
packages/core/src/widgets/number/NumberControl.tsx	97.82% <100.00%> (+0.45%)	⬆️
packages/core/src/widgets/string/StringControl.tsx	100.00% <100.00%> (ø)
packages/core/src/widgets/text/TextControl.tsx	100.00% <100.00%> (ø)
packages/core/test/data/fields.mock.ts	100.00% <100.00%> (ø)

... and 14 files with indirect coverage changes