Markdown toggle button in WYSIWYG editor doesn't visually indicate state

[u9000-Nine]

Describe the bug

The Markdown toggle button in the WYSIWYG editor does not visually indicate it's state unless you hover over it.

Reproduction

1. Enable the WYSIWYG editor by pressing the Aa button in the message input box.
2. Toggle the Markdown button a couple times, making sure to focus/hover on a different button between each press.
3. Observe that the only visual change is the background color, which is dependent on hover, not state.

Expected behavior

The button's state would be visually indicated.

Platform and versions

1. OS: Windows 10
2. Browser: Helium version 0.9.4.1
3. Cinny version: v1.11.1 PWA

Additional context

No response