Adds type definition for koa-jwt (https://github.com/koajs/jwt) (#13440)

* Adding type definition for https://github.com/koajs/jwt

* Adding lint and fixing issues reported by it

* fixig issues

* fixing koa-jwt test

* Fixing tslint config and jwt return type.

* Updating code based on @andy-ms comments.

koa-jwt/index.d.ts

@@ -0,0 +1,21 @@
+// Type definitions for koa-jwt 2.1
+// Project: https://github.com/koajs/jwt
+// Definitions by: Bruno Krebs <https://github.com/brunokrebs/>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+import Koa = require("koa");
+
+export = jwt;
+
+declare function jwt(options: jwt.Options): Koa.Middleware;
+
+declare namespace jwt {
+    export interface Options {
+        secret: string | Buffer;
+        key?: string;
+        getToken?: (opts: jwt.Options) => string;
+        passthrough?: boolean;
+        cookie?: string;
+        debug?: boolean;
+    }
+}

koa-jwt/koa-jwt-tests.ts

@@ -0,0 +1,13 @@
+import koa = require('koa');
+import jwt = require('koa-jwt');
+
+var app = new koa();
+
+app.use(jwt({
+    secret: 'some-secret-key'
+}));
+
+app.use(jwt({
+    secret: 'some-secret-key',
+    key: 'auth'
+}));

koa-jwt/tsconfig.json

@@ -0,0 +1,19 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "target": "es6",
+        "noImplicitAny": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "koa-jwt-tests.ts"
+    ]
+}

koa-jwt/tslint.json

@@ -0,0 +1,3 @@
+{
+    "extends": "../tslint.json"
+}