Merge pull request #248 from coadan/236-extended-typescript-support

TypeScript <3.7 support by self-reference type rewrite

Author: dcousens

index.d.ts

@@ -10,6 +10,7 @@
 
 export type Value = string | number | boolean | undefined | null;
 export type Mapping = { [key: string]: any };
-export type Argument = Value | Mapping | Argument[];
+interface ArgumentArray extends Array<Value | Mapping | ArgumentArray>{}
+export type Argument = Value | Mapping | ArgumentArray;
 
 export default function classNames(...args: Argument[]): string;