Allow user to set timezone (#12775)

* Allow user to set timezone

* Update test snapshots

---------

Co-authored-by: Florian Duros <florianduros@element.io>

src/settings/Settings.tsx

@@ -649,6 +649,11 @@ export const SETTINGS: { [setting: string]: ISetting } = {
         displayName: _td("settings|always_show_message_timestamps"),
         default: false,
     },
+    "userTimezone": {
+        supportedLevels: LEVELS_DEVICE_ONLY_SETTINGS,
+        displayName: _td("settings|preferences|user_timezone"),
+        default: "",
+    },
     "autoplayGifs": {
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,
         displayName: _td("settings|autoplay_gifs"),