chgrp, chown: refer to each other and add example (#19793)

Author: Managor

pages/common/chgrp.md

@@ -1,6 +1,7 @@
 # chgrp
 
 > Change group ownership of files and directories.
+> See also: `chown`.
 > More information: <https://www.gnu.org/software/coreutils/manual/html_node/chgrp-invocation.html>.
 
 - Change the owner group of a file/directory:

pages/common/chown.md

@@ -1,6 +1,7 @@
 # chown
 
 > Change user and group ownership of files and directories.
+> See also: `chgrp`.
 > More information: <https://www.gnu.org/software/coreutils/manual/html_node/chown-invocation.html>.
 
 - Change the owner user of a file/directory:
@@ -15,6 +16,10 @@
 
 `sudo chown {{user}}: {{path/to/file_or_directory}}`
 
+- Change the group of a file to a group that the current user belongs to:
+
+`chown :{{group}} {{path/to/file_or_directory}}`
+
 - Recursively change the owner of a directory and its contents:
 
 `sudo chown {{[-R|--recursive]}} {{user}} {{path/to/directory}}`