Improved intergration/linking to external physical layout tools

[petejohanson]

Right now, two "external" projects exist that massively simplify implementing physical layouts (which are a prerequisite for Studio support for a board/shield):

• Cem's converter: https://zmk-physical-layout-converter.streamlit.app/
• Joel's position map tool: https://zmk-layout-helper.netlify.app/
• Nick's tool: https://nickcoutsos.github.io/keymap-layout-tools/

Cem's uses backend python, so is harder to directly integrate, but both are useful utilities we should somehow better integrate, or link to prominently in the right places in the docs.