fix(types): correct keys type in parseIndex parameter

The keys parameter in parseIndex was typed as ReadonlyArray<string>
but the serialized index from toJSON() contains full key objects
with path, id, weight, src, and getFn properties.

Closes #794

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: krisk

dist/fuse.d.ts

@@ -92,7 +92,13 @@ declare class Fuse<T> {
 
   public static parseIndex<U>(
     index: {
-      keys: ReadonlyArray<string>
+      keys: ReadonlyArray<{
+        path: string[]
+        id: string
+        weight: number
+        src: string | string[]
+        getFn?: (...args: any[]) => any
+      }>
       records: FuseIndexRecords
     },
     options?: FuseIndexOptions<U>

src/index.d.ts

@@ -92,7 +92,13 @@ declare class Fuse<T> {
 
   public static parseIndex<U>(
     index: {
-      keys: ReadonlyArray<string>
+      keys: ReadonlyArray<{
+        path: string[]
+        id: string
+        weight: number
+        src: string | string[]
+        getFn?: (...args: any[]) => any
+      }>
       records: FuseIndexRecords
     },
     options?: FuseIndexOptions<U>