Adding class comment

Author: schmidt-sebastian

Firestore/Example/Tests/SpecTests/FSTMockDatastore.m

@@ -152,6 +152,7 @@ - (instancetype)initWithDatabase:(FSTDatabaseInfo *)database
 
 @property(nonatomic, assign) BOOL open;
 @property(nonatomic, strong, readonly) NSMutableArray<NSArray<FSTMutation *> *> *sentMutations;
+
 @end
 
 @implementation FSTMockWriteStream

Firestore/Source/Remote/FSTDatastore.m

@@ -440,6 +440,7 @@ + (void)prepareHeadersForRPC:(GRPCCall *)rpc
 
 #pragma mark - GRXFilter
 
+/** Filter class that allows disabling of GRPC callbacks. */
 @interface GRXFilter : NSObject <GRXWriteable>
 
 - (instancetype)initWithStream:(FSTStream *)stream NS_DESIGNATED_INITIALIZER;