feat(tooltip): elevate z-index of tooltip when open

docs/src/pages/components/Tooltip.svx

@@ -4,7 +4,9 @@
   import Preview from "../../components/Preview.svelte";
 </script>
 
-### Default (icon-only, "bottom" direction)
+### Default
+
+By default, the tooltip is triggered by an information icon.
 
 <Tooltip tooltipBodyId="tooltip-body">
   <p id="tooltip-body">

src/Tooltip/Tooltip.svelte

@@ -171,7 +171,10 @@
     }
   }}" />
 
-<div {...$$restProps} style="{$$restProps.style}; position: relative;">
+<div
+  {...$$restProps}
+  style="{open ? 'z-index: 1;' : ''}{$$restProps.style}; position: relative;"
+>
   {#if !hideIcon}
     <div bind:this="{ref}" id="{triggerId}" class:bx--tooltip__label="{true}">
       <slot name="triggerText">{triggerText}</slot>