Fix citation modal width on mobile device (#4867)

* Modal width for mobile device

* Fix citation button font

* Add tests

* Style citation button

* Use calculated width

* Update tests

* Fit and finish

* Update snapshots

* Update entry

* Fix ESLint

Author: compulim

CHANGELOG.md

@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 -  Fixes [#4865](https://github.com/microsoft/BotFramework-WebChat/issues/4865). Fixed <kbd>CTRL</kbd> + <kbd>Z</kbd> should undo correctly, by [@compulim](https://github.com/compulim), in PR [#4861](https://github.com/microsoft/BotFramework-WebChat/issues/pull/4861)
 -  Fixes [#4863](https://github.com/microsoft/BotFramework-WebChat/issues/4863). Disable dark theme for link references until chat history has dark theme support, by [@compulim](https://github.com/compulim), in PR [#4864](https://github.com/microsoft/BotFramework-WebChat/pull/4864)
+-  Fixes [#4866](https://github.com/microsoft/BotFramework-WebChat/issues/4866). Citation modal show fill screen width on mobile device and various fit-and-finish, by [@compulim](https://github.com/compulim), in PR [#4867](https://github.com/microsoft/BotFramework-WebChat/pull/4867)
 
 ### Added