logout: add page (#15240)

pages/common/logout.md

@@ -0,0 +1,12 @@
+# logout
+
+> Exit a login shell.
+> More information: <https://www.gnu.org/software/bash/manual/bash.html#index-logout>.
+
+- Exit a login shell:
+
+`logout`
+
+- Exit a login shell and specify a return value:
+
+`logout {{N}}`