Add dark theme

[aloctavodia]

As we already have theme's names in Catalan, Spanish and English. I propose to call it "tumma" (dark in Finnish).

This is a possible template. But we can use other styles. One issue is that we have black or gray as defaults for many plots. So if the user use a dark style like this, plots may not look good.

***************************************************************************

* FIGURE *

***************************************************************************

figure.facecolor: black # broken white outside box
figure.edgecolor: None # broken white outside box
figure.titleweight: bold # weight of the figure title
figure.titlesize: 18

figure.figsize: 6, 5
figure.dpi: 200.0
figure.constrained_layout.use: True

***************************************************************************

* FONT *

***************************************************************************

font.style: normal
font.variant: normal
font.weight: normal
font.stretch: normal

text.color: .85

***************************************************************************

* AXES *

***************************************************************************

axes.facecolor: 0.05
axes.edgecolor: black # axes edge color
axes.linewidth: 0.8 # edge line width

axes.grid: False # do not show grid

axes.grid.axis: y # which axis the grid should apply to

axes.grid.which: major # grid lines at {major, minor, both} ticks
axes.axisbelow: True # keep grid layer in the back

grid.color: .2 # grid color
grid.linestyle: - # solid
grid.linewidth: 0.8 # in points
grid.alpha: 1.0 # transparency, between 0.0 and 1.0

lines.solid_capstyle: round

axes.spines.right: False # do not show right spine
axes.spines.top: False # do not show top spine

axes.titlesize: 16
axes.titleweight: bold # font weight of title

axes.labelsize: 14
axes.labelcolor: .85
axes.labelweight: normal # weight of the x and y labels

color-blind friendly cycle designed using https://colorcyclepicker.mpetroff.net/

see preview and check for colorblindness here https://coolors.co/008b92-f15c58-48cdef-98d81a-997ee5-f5dc9d-c90a4e-145393-ffffff-616161

axes.prop_cycle: cycler(color=["008b92", "f15c58", "48cdef", "98d81a", "997ee5", "f5dc9d", "c90a4e", "145393", "ffffff", "616161"])

image.cmap: viridis

***************************************************************************

* TICKS *

***************************************************************************

xtick.labelsize: 14
xtick.color: .85
xtick.top: False
xtick.bottom: True
xtick.direction: out

ytick.labelsize: 14
ytick.color: .85
ytick.left: True
ytick.right: False
ytick.direction: out

***************************************************************************

* LEGEND *

***************************************************************************

legend.framealpha: 0.5
legend.frameon: False # do not draw on background patch
legend.fancybox: False # do not round corners

legend.numpoints: 1
legend.scatterpoints: 1

legend.fontsize: 14

[imperorrp]

Having a dark theme sounds nice. Maybe we could switch the default colors based on theme for the plot artists

[aloctavodia]

Right, to do so, we will need to read the colors from the template, style sheet.