Creates a userspace for keymaps (#1559)

* create a user space

* adds example

* document, add readme.md

* jackhumbert userspace, ergodox keymap

users/jackhumbert/jackhumbert.h

@@ -0,0 +1,6 @@
+#ifndef USERSPACE
+#define USERSPACE
+
+#include "quantum.h"
+
+#endif