[Typography] Fix build breakage due to missing implementation of MDCB…

…asicFontScheme. (#3242)

This failure was introduced in 2e48edf.

components/schemes/Typography/src/MDCFontScheme.m

@@ -0,0 +1,20 @@
+/*
+ Copyright 2018-present the Material Components for iOS authors. All Rights Reserved.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import "MDCFontScheme.h"
+
+@implementation MDCBasicFontScheme	
+@end