test(tooltip): add unit tests

tests/Tooltip/TooltipEvents.test.svelte

@@ -0,0 +1,27 @@
+<script lang="ts">
+  import { Tooltip } from "carbon-components-svelte";
+
+  let openCount = 0;
+  let closeCount = 0;
+
+  function handleOpen() {
+    openCount += 1;
+  }
+
+  function handleClose() {
+    closeCount += 1;
+  }
+</script>
+
+<div>
+  <p>Open events: {openCount}</p>
+  <p>Close events: {closeCount}</p>
+
+  <Tooltip
+    iconDescription="Information"
+    on:open={handleOpen}
+    on:close={handleClose}
+  >
+    Interact with this tooltip to trigger events
+  </Tooltip>
+</div>