ICE40: Support for IceBreaker board

[Harvie]

Hello,
can you please add support for icebreaker board?
it's ICE40 based open hardware board readily available for reasonable price through several vendors.
It's also fully documented here: https://github.com/icebreaker-fpga/icebreaker

[lawrie]

There is already a simple version for the iCEBreaker - see https://github.com/SpinalHDL/SaxonSoc/tree/dev/hardware/synthesis/icebreaker

It is the same as the Up5k evaluation board example, apart from the synthesis.