Add terminus_mini keyboard and nyquist/DivergeJM layout (#1851)

Add terminus_mini keyboard and nyquist/DivergeJM layout (#1851)

* First commit of the Terminus_Mini firmware and the DivergeJM version of the Nyquist firmware

* Fix terminus_mini & nyquist/DivergeJM readme files

Previously an outdated copy of the default readme. Updated to match the  Nyquist/DivergeJM format (DivergeJM is a split 5x12 implementation of the terminus_mini layout)

* Update makefiles to rules.mk

Renamed both Makefiles to rules.mk, removed references to makefiles

* Updated rules.mk

Inadvertantly removed important code from the rules.mk in previous commit. This has been restored.

Also disabled Tap_Dance in both rules.mk files

* Moved terminus_mini to handwired

Realised that existing directory was not appropriate for the terminus_mini project, moved to handwired.