Update free-courses-id.md (#7634)

* Update free-courses-id.md

Added Linux Fundamentals Course in Indonesian

* revert: linux heading

Co-authored-by: Biswadeep Purkayastha <98874428+metabiswadeep@users.noreply.github.com>

* lint: leave 2 blank lines between listings and next heading

Co-authored-by: Biswadeep Purkayastha <98874428+metabiswadeep@users.noreply.github.com>

* lint: alphabetize

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>
Co-authored-by: Biswadeep Purkayastha <98874428+metabiswadeep@users.noreply.github.com>

courses/free-courses-id.md

@@ -274,6 +274,7 @@
 
 ### Linux
 
+* [Belajar linux fundamentals](https://youtube.com/playlist?list=PLbLqbqNn7VYpnd7FggSeq18AgE4gdsy2F) - ID-Networkers
 * [Linux Pemula](https://www.youtube.com/playlist?list=PLACzo3mGgHK_D2wkGu4AvUAQiqLC30PTz) - LINUXcare
 * [Tutorial Terminal Linux Bahasa Indonesia](https://www.youtube.com/playlist?list=PLy1BHEa_Wr-cpjWY5uOqsMxQwiQrRnC8B) - ArtAway