add MT6701 to main README

Author: Richard Unger

README.md

@@ -29,6 +29,7 @@ What's here? See the sections below. Each driver or function should come with it
  - [SC60228 SPI driver](src/encoders/sc60228/) - SPI driver for SemiMent SC60288 magnetic encoder IC.
  - [MA330 SPI driver](src/encoders/ma330/) - SPI driver for the MPS MagAlpha MA330 absolute position magnetic rotary encoder IC.
  - [MT6816 SPI driver](src/encoders/mt6816/) - SPI driver for the MagnTek MT6816 absolute position magnetic rotary encoder IC.
+ - [MT6701 SSI driver](src/encoders/mt6701/) - SSI driver for the MagnTek MT6701 absolute position magnetic rotary encoder IC.
 
 ### Communications