Python: Extend supported MIME types

When using Python 3.x together with a respective LSP
you may end up inside pyi files when using follow
symbol.
Ensure a more user-friendly handling of these files.

Change-Id: Ied6528f0ad0ac6090fe8873f33b6e1a73ab9a5de
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/python/Python.json.in

@@ -25,6 +25,11 @@
         \"        <comment>Python source file without console</comment>\",
         \"        <glob pattern=\'*.pyw\'/>\",
         \"    </mime-type>\",
+        \"    <mime-type type=\'text/x-python-interface\'>\",
+        \"        <sub-class-of type=\'text/x-python\'/>\",
+        \"        <comment>Python module interface file</comment>\",
+        \"        <glob pattern=\'*.pyi\'/>\",
+        \"    </mime-type>\",
         \"    <mime-type type=\'text/x-python-project\'>\",
         \"        <sub-class-of type=\'text/x-python\'/>\",
         \"        <comment>Qt Creator Python project file</comment>\",