fix: Add temporary backwards compatible setup.py

setup.py is maintained so that there is no hard dependency on bench
v5.11.0 and people get enough time to update their CLI. Hope the TODO
adds a subtle reminder for the future ;)

setup.py

@@ -0,0 +1,6 @@
+# TODO: Remove this file when bench >=v5.11.0 is adopted / v15.0.0 is released
+from setuptools import setup
+
+name = "frappe"
+
+setup()