Add gallery example for scatter plot with histograms on sides

[michaelgrund]

Description of proposed changes

This PR adds a new gallery example showing a combination of a scatter plot with histograms on the sides. This is often used but I found no documentation in the GMT universe for this use-case. Inspired by matplotlib.

Preview: https://pygmt-dev--2410.org.readthedocs.build/en/2410/gallery/histograms/scatter_and_histograms.html

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[michaelgrund]

/format

[michaelgrund]

/format

[michaelgrund]

I have undone the changes regarding frame=["wSrt", "x+a1", "y+lCounts"] since in my opinion it's nice to have ticks along the axis of the histograms.

[michaelgrund]

/format

[seisman]

I have undone the changes regarding frame=["wSrt", "x+a1", "y+lCounts"] since in my opinion it's nice to have ticks along the axis of the histograms.

I think what you should use is xf1, not x+a1.

[michaelgrund]

/format

[michaelgrund]

Is the chosen "Histograms" category the right one for this example @GenericMappingTools/pygmt-maintainers ?

[yvonnefroehlich]

Is the chosen "Histograms" category the right one for this example @GenericMappingTools/pygmt-maintainers ?

I think the (more) interesting part of this figure are the histograms at the sides (not the scatter plot in the center), thus I would leave it as is in the "Histograms" category. There is also already a stand-alone gallery example for a Scatter plot.

[weiji14]

Nice example! Just two minor suggestions.