extrepo: add page (#10876)

* extrepo: add page

---------

Co-authored-by: Vysakh Premkumar <vysakhpr218@gmail.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/linux/extrepo.md

@@ -0,0 +1,21 @@
+# extrepo
+
+> Manage external Debian repositories.
+> It is used to manage external repositories in Debian.
+> More information: <https://manned.org/extrepo.1p>.
+
+- Search for a given package:
+
+`extrepo search {{package}}`
+
+- Enable the repository:
+
+`sudo extrepo enable {{repository_name}}`
+
+- Disable the repository:
+
+`sudo extrepo disable {{repository_name}}`
+
+- Update the repository:
+
+`sudo extrepo update {{repository_name}}`