Android course added (#7700)

* Android course added

* Update free-courses-en.md

* Update free-courses-en.md

* Update free-courses-en.md

* removed youtube

* Update free-courses-en.md

courses/free-courses-en.md

@@ -160,6 +160,7 @@
 * [Android Developer Fundamentals (Version 2) — Codelab](https://developer.android.com/courses/fundamentals-training/toc-v2)
 * [Android Developer Fundamentals (Version 2) — Concepts](https://google-developer-training.github.io/android-developer-fundamentals-course-concepts-v2/index.html)
 * [Android Performance](https://www.udacity.com/course/android-performance--ud825) (Udacity)
+* [Android with kotlin](https://youtube.com/playlist?list=PLlxmoA0rQ-Lw5k_QCqVl3rsoJOnb_00UV) - Smartherd
 * [Build Native Mobile Apps with Flutter](https://www.udacity.com/course/build-native-mobile-apps-with-flutter--ud905) (Udacity)
 * [CS194A Android Development](https://www.youtube.com/playlist?list=PL7NYbSE8uaBDcLkbXsQADdvBnVbavonGn) - Rahul Pandey (Stanford)
 * [CS50 2019 - Android Track](https://www.youtube.com/playlist?list=PLhQjrBD2T381qULidYDKP55-4u1piASC1) - David J. Malan (Harvard OpenCourseWare)