Add missing FunctionNode.name to Typescript types

Author: Josh Hansen

types/index.d.ts

@@ -233,6 +233,7 @@ declare namespace math {
   interface FunctionNode extends MathNodeCommon {
     type: 'FunctionNode';
     isFunctionNode: true;
+    name: string;
     fn: SymbolNode;
     args: MathNode[];
   }