WIP: Intros / Tutorials / Gallery: Include folder in colormap name

[yvonnefroehlich]

Description of proposed changes

Include the folder (https://github.com/GenericMappingTools/gmt/tree/master/share/cpt) in the colormap name in the examples

• intros
• tutorials
• gallery
• src
• tests
• datasets
• technical references
• contributing guide

Fixes #4308

Preview:

Guidelines

• General Guidelines for Pull Request
• Guidelines for Contributing Documentation
• Guidelines for Contributing Code

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash command is:

• /format: automatically format and lint the code

[seisman]

Still need to update following lines:

pygmt/src/grd2cpt.py:180:        a categorical color table, like ``cmap="categorical"``.
pygmt/src/makecpt.py:165:        a categorical color table, like ``cmap="categorical"``.
pygmt/tests/test_makecpt.py:149:    makecpt(cmap="categorical", categorical=True, series=[0, 6, 1])
doc/techref/justification_codes.md:108:fig.colorbar(cmap="buda", frame=0, position="jMC+w10c/2c+h")
doc/contributing.md:692:    fig_ref.grdimage("@earth_relief_01d_g", projection="W120/15c", cmap="geo")
doc/contributing.md:693:    fig_test.grdimage(grid, projection="W120/15c", cmap="geo")

Perhaps also update turbo to google/turbo in the following lines:

pygmt/datasets/mercury_relief.py:62:    ``cmap="@mercury_relief.cpt"``, otherwise GMT's default CPT (*turbo*) will be used.
pygmt/datasets/earth_age.py:50:    ``cmap="@earth_age.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/moon_relief.py:63:    ``cmap="@moon_relief.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/earth_mean_dynamic_topography.py:48:    ``cmap="@earth_mdt.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/pluto_relief.py:61:    ``cmap="@pluto_relief.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/earth_mean_sea_surface.py:50:    ``cmap="@earth_mss.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/mars_relief.py:63:    ``cmap="@mars_relief.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/venus_relief.py:50:    ``cmap="@venus_relief.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/earth_dist.py:50:    ``cmap="@earth_dist.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/earth_relief.py:70:    dataset-specific CPT when plotting the dataset, explicitly set ``cmap="geo"``,
pygmt/datasets/earth_deflection.py:58:    ``cmap="@earth_defl.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
pygmt/datasets/earth_vertical_gravity_gradient.py:50:    ``cmap="@earth_vgg.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If

[seisman]

Looks good to me except two typos.