Adding support for SpeechRate common term

We added nested JSON objects support to the GPII/ORCA settings handler.
(see commit [1]). You should check that you're using a copy of the linux
repo which includes this commit.

[1]: https://github.com/javihernandez/linux/commit/3c64ab6d67c2a5056045927e87f673f41cc0f73c