rev: add page (#18171)

pages/osx/rev.md

@@ -0,0 +1,12 @@
+# rev
+
+> Reverse lines of text.
+> More information: <https://keith.github.io/xcode-man-pages/rev.1.html>.
+
+- Reverse each line in a file to `stdout`:
+
+`rev {{path/to/file}}`
+
+- Reverse each line from `stdin` to `stdout`:
+
+`{{command}} | rev`