add pretixplugin.toml

pretixplugin.toml

+[plugin]
+package = "pretix-keycloak-create-user"
+modules = [ "pretix_keycloak_create_user" ]
+marketplace_name = "keycloak-create-user"

setup.cfg

@@ -36,6 +36,7 @@ exclude_lines =
 ignore =
     .update-locales.sh
     .install-hooks.sh
+    pretixplugin.toml
     Makefile
     manage.py
     tests/*