chsh, chpass: add pages; pages/linux/chsh: update page (#12160)

* chpass, chsh: add page for {Free,Net,Open}BSD and update common page

* pages.*BSD: add aliases for chpass

* chpass: add page for osx

pages/linux/chsh.md

@@ -0,0 +1,21 @@
+# chsh
+
+> Change user's login shell.
+> Part of `util-linux`.
+> More information: <https://manned.org/chsh>.
+
+- Set a specific login shell for the current user interactively:
+
+`sudo chsh`
+
+- Set a specific login [s]hell for the current user:
+
+`sudo chsh --shell {{path/to/shell}}`
+
+- Set a login [s]hell for a specific user:
+
+`sudo chsh --shell {{path/to/shell}} {{username}}`
+
+- [l]ist available shells:
+
+`sudo chsh --list-shells`