linter 5.0 compat (#117)

Author: f3ath

lib/fun_extra.dart

@@ -1,5 +1,5 @@
 /// A collection of semi-useful non-standard functions for JSONPath.
-library fun_extra;
+library;
 
 export 'package:json_path/src/fun/extra/index.dart';
 export 'package:json_path/src/fun/extra/is_array.dart';

lib/fun_sdk.dart

@@ -1,5 +1,5 @@
 /// An SDK for building custom functions for JSONPath.
-library fun_sdk;
+library;
 
 export 'package:json_path/src/expression/nodes.dart';
 export 'package:json_path/src/fun/fun.dart';

lib/json_path.dart

@@ -1,5 +1,5 @@
 /// JSONPath for Dart
-library json_path;
+library;
 
 export 'package:json_path/src/json_path.dart';
 export 'package:json_path/src/json_path_match.dart';