This renaming follows the decision taken at the General Assemblee of January 27th 2021 (cf. https://repos.goffi.org/sat_docs/raw-file/tip/association/2021-01-27%20-%20compte%20rendu%20de%20l%27AG%20extraordinaire.pdf)
recursive_update
- a new `utils` module has been added for backend and frontends generic utilities - per_luminance method calculate the perceived luminance of a colour (is it dark or light?). This is useful to automatically select the suitable colour in a theme.
