add quality MERN STACK course to courses/free-courses-vi.md (#11181)

* add src link to contribute for everyone who can access

* add src link to contribute for everyone who can access

* add src link to contribute for everyone who can access

* add src link to contribute for everyone who can access

courses/free-courses-vi.md

@@ -308,6 +308,7 @@
 * [Đồ án Web môi giới](https://www.youtube.com/playlist?list=PLiyVagO7GfBE1j4vjp-QLc1KHR1LPIl3G) - J2Team
 * [Lập Trình Web Chuyên Sâu](https://www.youtube.com/playlist?list=PLiyVagO7GfBE1l9XIGemSpy8bnm7QDmsY) - J2Team
 * [Lập Trình Web Cơ Bản](https://www.youtube.com/playlist?list=PLiyVagO7GfBE3_b-4lJEVk7iq1pHQ-xcM) - J2Team
+* [MERN PRO • Học lập trình Front-end + Back-end | Làm dự án thực tế Trello kéo thả](https://www.youtube.com/playlist?list=PLP6tw4Zpj-RJP2-YrhtkWqObMQ-AA4TDy) - TrungQuanDev - Một Lập Trình Viên
 
 
 ### Wordpress