added grid rotation to norns module api

[filipforsstrom]

first time contributing (open for any feedback)

this commit adds docs for norns grid rotation function. used same language as found in the lua file

[tehn]

thanks!

this API doc is actually copied directly from the norns repository--- it's autogenerated by ldoc based on the lua files.

looks like the rotation is here:

https://github.com/monome/norns/blob/main/lua/core/grid.lua#L83

which means the docs need to be regenerated and copied over to the web docs repo.

thanks for spotting this!