[Feature] Support HTML-in-Markdown (#5161)

* Added betterLinkDocumentMod

* add markdownRenderHTML to styleOptions

* Use new betterLinkDocumentMod and add a test

* Fix asButton with aria-label and className

* Update snapshots

* Update entry

* Use DOMParser + XMLSerializer

* Revert red box

* Update CHANGELOG.md

* Update CHANGELOG.md

Removes the redundant second changelog line

* Add breaking changes

* Run in JSDOM and remove empty "title" attribute

* More explanation

* Add HTML-in-Markdown for Adaptive Cards

* Style HTML-in-Markdown for Adaptive Cards

* Fix tests

* Revert containerClassName

* Move container to useRenderMarkdownAsHTML

* Fix tests

* Fix tests

* Clean up

* Add comment

* Update entry

* Fix tests

* Added open in external icon

* Add newline to end of XML serialization

* Better test

* Add HTML-in-Markdown

---------

Co-authored-by: William Wong <compulim@users.noreply.github.com>
Co-authored-by: Benjamin Yackley <beyackle@microsoft.com>
Co-authored-by: Eugene Olonov <eolonov@gmail.com>

Author: 4 people

CHANGELOG.md

@@ -35,6 +35,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 -  Removed deprecated code: `connect*`, `useRenderActivity`, `useRenderActivityStatus`, `useRenderAvatar`, in PR [#5148](https://github.com/microsoft/BotFramework-WebChat/pull/5148), by [@compulim](https://github.com/compulim)
 -  Added named exports in both CommonJS and ES Modules module format, in PR [#5148](https://github.com/microsoft/BotFramework-WebChat/pull/5148), by [@compulim](https://github.com/compulim)
 -  Removed deprecated `useFocusSendBox()` hook, please use `useFocus('sendBox')` instead, in PR [#5150](https://github.com/microsoft/BotFramework-WebChat/pull/5150), by [@OEvgeny](https://github.com/OEvgeny)
+-  HTML-in-Markdown is now supported. To disable this feature, set `styleOptions.markdownRenderHTML` to `false`
 
 ### Added
 
@@ -65,6 +66,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 -  Added `<ThemeProvider>` component to apply theme pack to Web Chat, by [@compulim](https://github.com/compulim), in PR [#5120](https://github.com/microsoft/BotFramework-WebChat/pull/5120)
 -  Added `useMakeThumbnail` hook option to create a thumbnail from the file given, by [@compulim](https://github.com/compulim), in PR [#5123](https://github.com/microsoft/BotFramework-WebChat/pull/5123) and [#5122](https://github.com/microsoft/BotFramework-WebChat/pull/5122)
 -  Added `moduleFormat` and `transpiler` build info to `<meta>` tag, in PR [#5148](https://github.com/microsoft/BotFramework-WebChat/pull/5148), by [@compulim](https://github.com/compulim)
+-  Added support of rendering HTML-in-Markdown, in PR [#5161](https://github.com/microsoft/BotFramework-WebChat/pull/5161), by [@compulim](https://github.com/compulim), [@beyackle2](https://github.com/beyackle2), and [@OEvgeny](https://github.com/OEvgeny)
 
 ### Fixed
 

README.md

@@ -54,6 +54,12 @@ export default function MyComponent() {
 }
 ```
 
+#### Support HTML-in-Markdown
+
+Web Chat will now render HTML-in-Markdown. We have ported our sanitizer and accessibility fixer to work on HTML level. Both Markdown and HTML-in-Markdown will receive the same treatment and meet our security and accessibility requirements.
+
+You can turn off this option by setting `styleOptions.markdownRenderHTML` to `false`.
+
 ### 4.16.1 notable changes
 
 Web Chat now supports [Adaptive Cards schema up to 1.6](https://adaptivecards.io/explorer/). Some features in Adaptive Cards are in preview or designed to use outside of Bot Framework. Web Chat does not support these features.