feat(Breadcrumb): create new entity that contains logic related to breadcrumb-like navigation

src/entities/Breadcrumb/model/index.ts

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+export * from './store/scrollBreadcrumbsStore.svelte';

src/entities/Breadcrumb/model/store/scrollBreadcrumbsStore.svelte.ts

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+import type { Snippet } from 'svelte';
+
+export interface BreadcrumbItem {
+    index: number;
+    title: Snippet<[{ className?: string }]>;
+}
+
+class ScrollBreadcrumbsStore {
+    #items = $state<BreadcrumbItem[]>([]);
+
+    get items() {
+        // Keep them sorted by index for Swiss orderliness
+        return this.#items.sort((a, b) => a.index - b.index);
+    }
+    add(item: BreadcrumbItem) {
+        if (!this.#items.find(i => i.index === item.index)) {
+            this.#items.push(item);
+        }
+    }
+    remove(index: number) {
+        this.#items = this.#items.filter(i => i.index !== index);
+    }
+}
+
+export function createScrollBreadcrumbsStore() {
+    return new ScrollBreadcrumbsStore();
+}
+
+export const scrollBreadcrumbsStore = createScrollBreadcrumbsStore();