Migrate CustomRender to HtmlExtension

[Sub6Resources]

Closes #1142

Getting started on this. Here's a task list for myself. Any additional feedback/suggestions are still welcome.

• Write HtmlExtension class
• Write ExtensionContext class
• Integrate HtmlExtension into the Html widget flow
• Write TagExtension helper class
• Write MatcherExtension helper class
• Rewrite flutter_html_audio to use HtmlExtension
• Rewrite flutter_html_iframe to use HtmlExtension
• Rewrite flutter_html_math to use HtmlExtension
• Rewrite flutter_html_svg to use HtmlExtension
• Rewrite flutter_html_table to use HtmlExtension
• Rewrite flutter_html_video to use HtmlExtension
• Write ImageExtension class
• Bump version to 3.0.0-beta.1
• Add migration guide
• Add better documentation for HtmlExtension

Fixes #1137
Closes #717 Closes #1134 Closes #1105

Fixes #1206. Fixes #1199. Fixes #1180. Fixes #1113

[codecov]

Codecov Report

Patch coverage: 77.09% and project coverage change: +5.76 🎉

Comparison is base (c75e0df) 51.40% compared to head (3ed46cf) 57.16%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1176      +/-   ##
==========================================
+ Coverage   51.40%   57.16%   +5.76%     
==========================================
  Files          19       36      +17     
  Lines        2640     2610      -30     
==========================================
+ Hits         1357     1492     +135     
+ Misses       1283     1118     -165     

Impacted Files	Coverage Δ
lib/src/anchor.dart	66.66% <ø> (ø)
lib/src/extension/helpers/image_extension.dart	0.00% <0.00%> (ø)
lib/src/extension/helpers/image_tap_extension.dart	0.00% <0.00%> (ø)
lib/src/style.dart	84.87% <0.00%> (ø)
lib/src/utils.dart	77.27% <ø> (ø)
lib/src/builtins/details_element_builtin.dart	11.11% <11.11%> (ø)
lib/src/tree/styled_element.dart	23.68% <23.68%> (ø)
lib/src/extension/helpers/matcher_extension.dart	53.84% <53.84%> (ø)
lib/src/builtins/interactive_element_builtin.dart	54.76% <54.76%> (ø)
lib/src/extension/extension_context.dart	55.17% <55.17%> (ø)
... and 20 more

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[PritamSangani]

Hi @Sub6Resources - is there anything the community can do to help get this PR finished and a new major version released?

[Sub6Resources]

Continuing from #1153

[Sub6Resources]

Migrating to Extension has touched pretty much all of the codebase, so I've taken the opportunity to remove some technical debt and fix bugs as I found them.

Here's a summary of major changes in this PR so far (this list is a work in progress):

• Removed SelectableHtml (users should now use SelectionArea provided by Flutter). See breaking: Remove SelectableHtml #1153. Fixes [Investigate] Remove SelectableText in favor of SelectionArea? #1137
• Upgrades dependencies in all the sub-packages (fixes [MIGARATE] Migrate to latest webview_flutter plugin to 4.0.0 version #1206, fixes [FEATURE] Pls upgrade version "flutter_svg" to "1.1.1+1" #1113)
• Improvements to <table> code. Fixes [BUG] Borders on table cells are applied to underlying text #1199
• Simplify <img> code. Removes default loading animation. (fixes 加载图片，有了loadding,是否有属性可以去掉 #1180)

[Sub6Resources]

This pull request is ready. Just needs some additional documentation on the Wiki. Anybody that's just stopping in, please review! I'd love to get this release out sometime tomorrow!

[PritamSangani]

There was a comment made on the initial extension api RFC issue about the name of the api, with Extension potentially being confusing and leading to conflicts with it being quite generic. A suggestion was made to change to something like HtmlExtension. I was wondering if you had any thoughts on this.

re: #1142 (comment)

[Sub6Resources]

@PritamSangani Thanks for pointing that out. I had forgotten about that comment (although I had named all the extension packages as if I had already made the change -- IframeHtmlExtension for example).

I agree! Just updated from Extension to HtmlExtension

[Sembauke]

congrats 🥳