feat(ui-shell): HeaderAction supports tooltip (#2111)

Closes #2110

types/UIShell/HeaderAction.svelte.d.ts

@@ -25,12 +25,26 @@ type $Props = {
   closeIcon?: any;
 
   /**
-   * Specify the text.
+   * Specify the text displayed next to the icon.
    * Alternatively, use the named slot "text" (e.g., `<div slot="text">...</div>`)
    * @default undefined
    */
   text?: string;
 
+  /**
+   * Specify an icon tooltip. The tooltip will not be displayed
+   * if either the `text` prop or a named slot="text" is used
+   * @default undefined
+   */
+  iconDescription?: string;
+
+  /**
+   * Set the alignment of the tooltip relative to the icon.
+   * Only applies when `iconDescription` is provided
+   * @default "center"
+   */
+  tooltipAlignment?: "start" | "center" | "end";
+
   /**
    * Obtain a reference to the button HTML element
    * @default null