Initial commit with files

Still need to fix the imports

src/lib/internal/StackContextProvider.svelte

@@ -0,0 +1,42 @@
+<script lang="ts" context="module">
+    export enum StackMessage {
+        Add,
+        Remove,
+    }
+</script>
+
+<script lang="ts">
+    import { getContext, setContext } from "svelte";
+    import { writable, Writable } from "svelte/store";
+    type OnUpdate = (
+        message: StackMessage,
+        element: HTMLElement | null
+    ) => void;
+
+    export let onUpdate: OnUpdate | undefined;
+    export let element: HTMLElement | null;
+
+    let parentUpdateStore: Writable<OnUpdate> | undefined =
+        getContext("StackContext");
+    let notifyStore: Writable<OnUpdate> = writable(() => {});
+    setContext("StackContext", notifyStore);
+
+    $: notifyStore.set((...args: Parameters<OnUpdate>) => {
+        // Notify our layer
+        onUpdate?.(...args);
+
+        // Notify the parent
+        $parentUpdateStore?.(...args);
+    });
+
+    $: _cleanup = (() => {
+        if (_cleanup) {
+            _cleanup();
+        }
+        if (!element) return null;
+        $notifyStore(StackMessage.Add, element);
+        return () => $notifyStore(StackMessage.Remove, element);
+    })();
+</script>
+
+<slot />