The automatically chosen color is now the default value under `stylix.palette`,
rather than `null`.
The colors from `stylix.palette` are collected to make the default value
of `stylix.base16Scheme`.
If `stylix.base16Scheme` is overridden to an external file, the colors
from that file will NOT be written back to `stylix.palette`. For that
reason, you must still only refer to `lib.stylix.colors` within modules.
This does not rely on an external library for colour selection,
therefore it can be fine-tuned to create a better theme.
Closes#2 because Colorgram is no longer used.
