Add update_renpy_json.sh script.

To copy renpy.json from Ren'Py.

Author: renpytom

scripts/README.rst

@@ -0,0 +1,9 @@
+This directory contians scripts used to help maintain the project.
+
+
+update_renpy_json.sh
+--------------------
+
+Run this script to update the `renpy.json` file, by copying it from Ren'Py into this project. The file
+must first be updated in Ren'Py by building the spinx documentation. This takes a single argument, the
+path to the Ren'Py checkout.