Applying the snake_case convention throughout the repo (#967)

* Applying the snake_case convention throughout the repo

- Also removing the file extension where not needed
- Adding {{ }} on a few old pages

* Addressing concerns

- Added {{ }} where they were missed out
- Removed spaces inside {{ }}
- Reverting "file" to "filename" to make it clearer

* Fixing the comments on nc page

pages/linux/mkfs.fat.md

@@ -8,11 +8,11 @@
 
 - Create filesystem with a volume-name:
 
-`mkfs.fat -n {{volume-name}} {{/dev/sdb1}}`
+`mkfs.fat -n {{volume_name}} {{/dev/sdb1}}`
 
 - Create filesystem with a volume-id:
 
-`mkfs.fat -i {{volume-id}} {{/dev/sdb1}}`
+`mkfs.fat -i {{volume_id}} {{/dev/sdb1}}`
 
 - Use 5 instead of 2 file allocation tables: