added limits to suggestions of collection and file name search

lib/db/files_db.dart

@@ -1179,6 +1179,7 @@ class FilesDB {
       table,
       where: '$columnTitle LIKE ?',
       whereArgs: ["%$query%"],
+      limit: 20,
     );
     final files = _convertToFiles(results);
     return files;

lib/services/collections_service.dart

@@ -202,7 +202,9 @@ class CollectionsService {
         )
         .toList();
     List<CollectionWithThumbnail> result = [];
-    for (Collection collection in matchedCollection) {
+    const int limit = 20;
+    for (int i = 0; i < limit; i++) {
+      Collection collection = matchedCollection[i];
       result.add(
         CollectionWithThumbnail(
           collection,