Add dual end stop support

[alphaonex86]

Please describe the feature you would like implemented
Actually only ESP32 is fast to support dual end stop + stop the move and return, but actually it support only 1 end stop.
I wish support min end stop and max end stop, if min trigger do x++ to be safe, if max trigger do x-- to be safe.

Why do you think this would improve Grbl_ESP32?
If the machine start with end stop enable, it know in which way have to go

What do you need the feature for?
If the machine start with end stop enable, it know in which way have to go

Will this feature appear to a lot of users?
yes

[bdring]

Grbl_ESP32 is no longer supported. FluidNC is the new version of Grbl_ESP32.