[models] check in empty .inferconfig

Summary:
This is to make sure we do not influence the analysis of the models by accident
when a .inferconfig exists in some directory higher up (eg, `$HOME`, infer/,
...).

Reviewed By: sblackshear

Differential Revision: D7686136

fbshipit-source-id: 9a250ff

infer/models/.inferconfig

@@ -0,0 +1 @@
+{}