Added definition files for koa-json (#8873)

koa-json/koa-json-tests.ts

@@ -0,0 +1,15 @@
+/// <reference path="../koa/koa.d.ts" />
+/// <reference path="koa-json.d.ts" />
+
+import * as Koa from "koa";
+import * as json from 'koa-json';
+
+const app = new Koa();
+
+app.use(json({
+    pretty: false,
+    param: 'pretty',
+    spaces: 2
+}));
+
+app.listen(80)

koa-json/koa-json.d.ts

@@ -0,0 +1,40 @@
+// Type definitions for koa-json v2.x
+// Project: https://github.com/koajs/json
+// Definitions by: Alex Friedman <https://github.com/brooklyndev/>
+// Definitions: https://github.com/brooklyndev/DefinitelyTyped
+
+/* =================== USAGE ===================
+
+    import * as Koa from 'koa';
+    import * as json from 'koa-json';
+    
+    const app = new Koa();
+    app.use(json());
+
+ =============================================== */
+/// <reference path="../koa/koa.d.ts" />
+
+declare module "koa-json" {
+    
+    import * as Koa from "koa";
+    
+    function json(opts?:{
+        
+        /** 
+         * default to pretty response [true]
+        */
+        pretty?: boolean,
+        
+        /**
+         * optional query-string param for pretty responses [none]
+         */
+        param?: string,
+        
+        /**
+         * JSON spaces [2]
+         */
+        spaces?: number
+    }) : { (ctx: Koa.Context, next?: () => any): any } ;
+    namespace json {}
+    export = json;
+}