added computer networks in index and two course in free-courses-hi.md (#7311)

* added computer networks in index and two course in it

* Update courses/free-courses-hi.md

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

* Update courses/free-courses-hi.md

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

* Update free-courses-hi.md

* changed "Computer Networks" to "Network"

* chore: most common category name is Networking, not Network

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

courses/free-courses-hi.md

@@ -32,6 +32,7 @@
 * [Linux](#linux)
 * [Machine Learning](#machine-learning)
 * [Mathematics](#mathematics)
+* [Networking](#networking)
 * [Operating Systems](#operating-systems)
 * [PHP](#php)
 * [Python](#python)
@@ -299,6 +300,12 @@
 * [Statistics And Probability](https://www.youtube.com/playlist?list=PLU6SqdYcYsfLRq3tu-g_hvkHDcorrtcBK) - Gajendra Purohit
 
 
+### Networking
+
+* [3.4 Computer Networks (Complete Playlist)](https://www.youtube.com/playlist?list=PLmXKhU9FNesSjFbXSZGF8JF_4LVwwofCd) - Knowledge Gate
+* [Computer Networks (Complete Playlist)](https://www.youtube.com/playlist?list=PLxCzCOWd7aiGFBD2-2joCpWOLUrDLvVV_) - Gate Smashers, `tch.:` Varun Singla
+
+
 ### Operating Systems
 
 * [Operating System (Complete Playlist)](https://www.youtube.com/playlist?list=PLxCzCOWd7aiGz9donHRrE9I3Mwn6XdP8p) - Gate Smashers