fix(docs): Fix list of browser bugs and add virtual backgrounds for safari

Signed-off-by: Joas Schilling <coding@schilljs.com>

docs/user-requirements.md

@@ -11,15 +11,16 @@
 
 * Brave: latest
 * Chrome / Chromium: 49 or later
-	- Screensharing requires version 72 or later or this [Chrome extension](https://chrome.google.com/webstore/detail/screensharing-for-nextclo/kepnpjhambipllfmgmbapncekcmabkol)
+    - Screensharing requires version 72 or later or this [Chrome extension](https://chrome.google.com/webstore/detail/screensharing-for-nextclo/kepnpjhambipllfmgmbapncekcmabkol)
 * Edge: latest
-  - Speakers are not promoted
-  - Name changes while a call is ongoing are not reflected
+    - Speakers are not promoted
+    - Name changes while a call is ongoing are not reflected
 * Firefox / Firefox ESR: 52 or later
-  - Screensharing requires Firefox 66 or later
+    - Screensharing requires Firefox 66 or later
 * Opera: 72 or later
 * Safari: 13 or later
-  - Safari 12 also works in general, but users can not share their own screen
+    - Safari does not support virtual backgrounds and background blurring
+    - Safari 12 also works in general, but users can not share their own screen
 
 ## Mobile apps