Extend the gulp-autoprefixer Options type (#37671)

* Extend the gulp-autoprefixer Options type

* Fix TypeScript version

types/gulp-autoprefixer/index.d.ts

@@ -1,16 +1,24 @@
 // Type definitions for gulp-autoprefixer
 // Project: https://github.com/sindresorhus/gulp-autoprefixer
-// Definitions by: Asana <https://asana.com>
+// Definitions by: Asana <https://asana.com>, Jordy van Dortmont <https://github.com/jordyvandortmont>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 2.2
 
 /// <reference types="node"/>
 
 
 declare namespace autoPrefixer {
     interface Options {
-        browsers?: string[];
+        env?: string;
         cascade?: boolean;
+        add?: boolean;
         remove?: boolean;
+        supports?: boolean;
+        flexbox?: boolean|"no-2009";
+        grid?: false|"autoplace"|"no-autoplace";
+        stats?: object;
+        browsers?: string[];
+        ignoreUnknownVersions?: boolean;
     }
 }