Add support for accent color
This adds support for the 9 accent colors supported by gnome-shell 47.
The current hard-coded color will be replaced by the accent color defined by gnome shell's settings, the selection color will be a bit darker than the accent color in dark mode, and a bit lighter in light mode.
The reasoning for the increased contrast is that it allows the value inside the cells to stand out more, and the matching number highlighting has even more contrast additionally because it appears more often. The standalone accent color is already great to allow labels to stand out, so it's going unmodified.
Preview
PreviewI'll leave this open for a few days to play with it and in case you have any feedback.
Edited by Johan G.