Fix "Copy | Look Up" popup issue on mobile device (#2406)

public/index.html

@@ -108,6 +108,7 @@
           Roboto, Helvetica, Arial, sans-serif;
         font-family: var(--ui-font);
         -webkit-text-size-adjust: 100%;
+        -webkit-user-select: none;
         user-select: none;
         width: 100vw;
         height: 100vh;