chore: define input object type

Author: gajus

src/createObjectExpression.js

@@ -4,7 +4,10 @@ import BabelTypes, {
   ObjectExpression
 } from 'babel-types';
 
-const createObjectExpression = (t: BabelTypes, object: Object): ObjectExpression => {
+type InputObjectType = {
+  [key: string]: string | InputObjectType
+};
+const createObjectExpression = (t: BabelTypes, object: InputObjectType): ObjectExpression => {
   const properties = [];
 
   for (const name of Object.keys(object)) {