uctx: Document add_stop method and add linear_gradient example (!182) · Merge requests · flow3r / flow3r firmware · GitLab

Added documentation to add_stop based on: https://git.flow3r.garden/flow3r/flow3r-firmware/-/blob/main/components/micropython/usermodule/mp_uctx.c#L447

Example taken from: https://pippin.gimp.org/tmp/flow3r-logo.py