This function is called when a keypress has come in, before it is processed. The keycode should be one of `QK_STENO_BOLT`, `QK_STENO_GEMINI`, or one of the `STN_*` key values.
This function is called after a key has been processed, but before any decision about whether or not to send a chord. This is where to put hooks for things like, say, live displays of steno chords or keys.