added bip21 typedefinition

bip21/bip21-tests.ts

@@ -0,0 +1,9 @@
+/// <reference path='bip21.d.ts' />
+
+let decoded:any = bip21.decode('bitcoin:1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH?amount=20.3&label=Foobar');
+ 
+let encoded:string = bip21.encode('1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH', {
+	amount: 20.3,
+	label: 'Foobar'
+}); 
+ 

bip21/bip21.d.ts

@@ -0,0 +1,13 @@
+// Type definitions for bip21 v1.1.2
+// Project: https://github.com/bitcoinjs/bip21
+// Definitions by: Stefan Huber <https://github.com/stefanhuber/>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+declare module bip21 {
+    export function decode(uri:string) : {address:string,amount?:number}; 
+    export function encode(address:string,options?:any) : string;
+}
+
+declare module "bip21" {
+    export = bip21;
+}