www/threema-web: update 2.5.5 to 2.6.2

* [feature] Add Belarusian translation
* [feature] Add link to Threema Desktop 2.0 for iOS users
* [fix] Fix beta link in work flavor ([#1220][i1220])
* [fix] Open external links in new tab ([#1220][i1220])
* [feature] Add support for displaying emoji reactions ([#1222][i1222])
* [change] Allow Safari when connecting an Android device
* [bug] Fix message info gap ([#1226][i1226])
* [change] Upgrade dependencies ([#1230][i1230])
* [change] Switch to NodeJS 20 ([#1230][i1230])

https://github.com/threema-ch/threema-web/compare/v2.5.5...v2.6.2