Avoid importing dart:io directly

[daohoangson]

No description provided.

[github-actions]

Demo app

Deployed 468ea77 to https://example-ggff59k8i-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 #449 (468ea77) into master (350e8d1) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #449   +/-   ##
=======================================
  Coverage   96.96%   96.96%           
=======================================
  Files          37       37           
  Lines        2666     2666           
=======================================
  Hits         2585     2585           
  Misses         81       81           

Impacted Files	Coverage Δ
packages/core/lib/src/core_widget_factory.dart	99.45% <100.00%> (ø)
packages/enhanced/lib/src/widget_factory.dart	96.80% <100.00%> (ø)

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