Initial commit with files

Still need to fix the imports

src/lib/components/tabs/TabPanel.svelte

@@ -0,0 +1,30 @@
+<script lang="ts">
+    import { onMount } from "svelte";
+    import { useTabsContext } from "./TabGroup.svelte";
+    import { useId } from "./use-id";
+
+    let api = useTabsContext("TabPanel");
+    let id = `headlessui-tabs-panel-${useId()}`;
+    let panelRef = null;
+
+    onMount(() => {
+        $api.registerPanel(panelRef);
+        return () => $api.unregisterPanel(panelRef);
+    });
+
+    $: myIndex = $api.panels.indexOf(panelRef);
+    $: selected = myIndex === $api.selectedIndex;
+
+    $: propsWeControl = {
+        id,
+        role: "tabpanel",
+        "aria-labelledby": $api.tabs[myIndex]?.id,
+        tabIndex: selected ? 0 : -1,
+    };
+</script>
+
+<div {...{ ...$$restProps, ...propsWeControl }} bind:this={panelRef}>
+    {#if selected}
+        <slot />
+    {/if}
+</div>