Fixed: chat zindex

Author: ZhaoJiSen

src/app/elements/chat/chat.component.scss

@@ -9,7 +9,7 @@ nz-float-button {
   position: fixed;
   bottom: 200px;
   right: 5px;
-  z-index: 1000;
+  z-index: 99999;
   cursor: move;
   user-select: none;
   overflow: visible;