Stepper enable invert ($4) is boolean in legacy, but axis mask in grblHAL

[StefanBruens]

Legacy:

https://github.com/gnea/grbl/blob/master/doc/csv/setting_codes_en_US.csv#L6

4 | Invert step enable pin | boolean | Inverts the stepper driver enable pin signal. -- | -- | -- | --

or: https://github.com/terjeio/grblHAL/blob/master/doc/markdown/settings.md#4---step-enable-invert-boolean

$4 - Step enable invert, boolean

Current code: https://github.com/grblHAL/core/blob/6d00f743f09db2a07adadf4dc996e3d55de37cdb/settings.c#L387

[terjeio]

I have updated the settings wiki page for this. I believe I should use the legacy version if compatibility level is > 1...