lndir: add page (#14044)

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

pages/linux/lndir.md

@@ -0,0 +1,8 @@
+# lndir
+
+> Create a shadow directory of symbolic links to another directory tree.
+> More information: <https://manned.org/lndir>.
+
+- Create a shadow directory in the current directory:
+
+`lndir {{path/to/directory}}`