Fix FwfhTextStyle usage within CupertinoPageScaffold

[daohoangson]

Related to #698

[github-actions]

Demo app

Deployed 944a7cb to https://example-g2i002evd-flutter-widget-from-html.vercel.app.

Quick links:

• supported/tags.html
• Hello World
• Hello World (core)
• Wordpress
• --web-renderer canvaskit
• --web-renderer html

[codecov]

Codecov Report

Merging #713 (944a7cb) into master (e21163c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #713   +/-   ##
=======================================
  Coverage   98.20%   98.20%           
=======================================
  Files          63       63           
  Lines        3835     3839    +4     
=======================================
+ Hits         3766     3770    +4     
  Misses         69       69           

Impacted Files	Coverage Δ
packages/core/lib/src/data/text_style.dart	100.00% <ø> (ø)
packages/fwfh_text_style/lib/fwfh_text_style.dart	91.52% <100.00%> (+0.37%)	⬆️

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