Add Geological CPT in the Docs

[Esteban82]

In #8778 8 geological CPT were included in GMT. We need to edit the docs to include these additions. I think that only this page has to be updated. https://docs.generic-mapping-tools.org/dev/reference/cpts.html

[yvonnefroehlich]

Nice addition! This means mention this group of CPTs and create an image showing these colormaps, something like:

or (to have no overlapping annotations the colorbars need to be quite long; when showing the numbers (lower row) there is still some overlapping annotations)

[Esteban82]

Yes, we probably will add something like that. I think it is better to do this once we have the new CPTs (see discussion here GenericMappingTools/gmtserver-admin#284).

[chhei]

Hi @yvonnefroehlich

or (to have no overlapping annotations the colorbars need to be quite long; when showing the numbers (lower row) there is still some overlapping annotations)

yes - Paul added the -Sa option to colorbar - see here. Slanted annotations help to alleviate the spacing issue at least a bit but certainly for the shorter intervals at stage level these will be unavoidable. One way would be to just use a subset of the CPT.