chore: update the style of help island in edgeless mode (#2244)

packages/component/src/theme/global.css

@@ -163,6 +163,7 @@ input {
   border-radius: 0; /*Solve the problem of rounded corners of the input box on ios*/
   outline: medium; /*Remove the default yellow border on mouse click*/
   background-color: transparent;
+  caret-color: var(--affine-primary-color);
 }
 
 input:-webkit-autofill {