Conversation Settings menu is not accessible via keyboard

[krallowski]

Description

The settings menu on the top right in the conversation element cannot be accessed via keyboard because it is not part of the tab order.

Steps to reproduce

1. Open a conversation
2. Press tab to tab through interactive elements and try to reach the dropdown arrow

Expected behavior

At some point the arrow gets focus and I can press enter to open the menu

Current behavior

Tabbing skips the element

Possible Solution

Add a button element to the icon:

mail/widgets/views/conversationSettingsMenu.php

Line 26 in 7540f91

<div class="dropdown d-inline-block">

Additional info

Appeared on Firefox, HumHub version 1.18