openbsd: add directory; openbsd/pkg_{add,info,delete}: add page (#10698)

* openbsd: add directory; openbsd/pkg_{add,info,delete}: add page (#10698) 

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>
Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/openbsd/pkg_add.md

@@ -0,0 +1,17 @@
+# pkg_add
+
+> Install/update packages in OpenBSD.
+> See also: `pkg_info`, `pkg_delete`.
+> More information: <https://man.openbsd.org/pkg_add>.
+
+- Update all packages, including dependencies:
+
+`pkg_add -u`
+
+- Install a new package:
+
+`pkg_add {{package}}`
+
+- Install packages from the raw output of `pkg_info`:
+
+`pkg_add -l {{path/to/file}}`