added Operating systems and two courses in free-courses-hi.md (#7316)

* added Operating systems and two courses in free-courses-hi.md

* corrected title

* removed yt annotations, corrected titles , added instrutctor name

* Update courses/free-courses-hi.md

Co-authored-by: Eric Hellman <eric@hellman.net>

* Update courses/free-courses-hi.md

Co-authored-by: Eric Hellman <eric@hellman.net>

Co-authored-by: Eric Hellman <eric@hellman.net>

courses/free-courses-hi.md

@@ -30,6 +30,7 @@
 * [Linux](#linux)
 * [Machine Learning](#machine-learning)
 * [Mathematics](#mathematics)
+* [Operating Systems](#operating-systems)
 * [PHP](#php)
 * [Python](#python)
     * [Django](#django)
@@ -280,6 +281,12 @@
 * [Statistics And Probability](https://www.youtube.com/playlist?list=PLU6SqdYcYsfLRq3tu-g_hvkHDcorrtcBK) - Gajendra Purohit
 
 
+### Operating Systems
+
+* [Operating System (Complete Playlist)](https://www.youtube.com/playlist?list=PLxCzCOWd7aiGz9donHRrE9I3Mwn6XdP8p) - Gate Smashers
+* [Operating Systems for Placements 2022](https://www.youtube.com/playlist?list=PLDzeHZWIZsTr3nwuTegHLa2qlI81QweYG) - CodeHelp - by Babbar
+
+
 ### PHP
 
 * [Core PHP (Hindi)](https://www.youtube.com/playlist?list=PLbGui_ZYuhigFdLdbSI2EM2MrJB7I0j-B) - Rajesh Kumar, Geeky Shows