Duplicate pwgen command to osx

pwgen is available on linux and OSX. This duplicates it to both
environments. This means you'll be able to use the reference on both.

pages/osx/pwgen.md

@@ -0,0 +1,15 @@
+# pwgen
+
+> Generate pronounceable passwords.
+
+- Generate random password with s[y]mbols:
+
+`pwgen -y {{length}}`
+
+- Generate secure, hard-to-memorize passwords:
+
+`pwgen -s {{length}}`
+
+- Generate password with at least one capital letter in them:
+
+`pwgen -c {{length}}`