Put always-on-screen widgets in top left

always-on-screen widgets now appear in the top-left where the
call preview normally is if you're not in the room that they're in.

Fixes https://github.com/vector-im/riot-web/issues/7007
Based off https://github.com/matrix-org/matrix-react-sdk/pull/2053

src/stores/ActiveWidgetStore.js

@@ -32,6 +32,9 @@ class ActiveWidgetStore {
 
         // A WidgetMessaging instance for each widget ID
         this._widgetMessagingByWidgetId = {};
+
+        // What room ID each widget is associated with (if it's a room widget)
+        this._roomIdByWidgetId = {};
     }
 
     setWidgetPersistence(widgetId, val) {
@@ -46,6 +49,10 @@ class ActiveWidgetStore {
         return this._persistentWidgetId === widgetId;
     }
 
+    getPersistentWidgetId() {
+        return this._persistentWidgetId;
+    }
+
     setWidgetCapabilities(widgetId, caps) {
         this._capsByWidgetId[widgetId] = caps;
     }
@@ -76,6 +83,18 @@ class ActiveWidgetStore {
             delete this._widgetMessagingByWidgetId[widgetId];
         }
     }
+
+    getRoomId(widgetId) {
+        return this._roomIdByWidgetId[widgetId];
+    }
+
+    setRoomId(widgetId, roomId) {
+        this._roomIdByWidgetId[widgetId] = roomId;
+    }
+
+    delRoomId(widgetId) {
+        delete this._roomIdByWidgetId[widgetId];
+    }
 }
 
 if (global.singletonActiveWidgetStore === undefined) {