Changelog entry for v0.18.0

[seisman]

Description of proposed changes

This PR adds the changelog entry for v0.18.0.

• Release checklist: Release PyGMT v0.18.0 #4289
• Changelog PR of previous minor release: Changelog entry for v0.17.0 #4121
• Preview:
  • https://pygmt-dev--4323.org.readthedocs.build/en/4323/changes.html
  • https://pygmt-dev--4323.org.readthedocs.build/en/4323/minversions.html

Checklist

• Add a new entry in doc/_static/version_switch.js for documentation switcher
• Add the version to the compatibility table doc/minversions.md
• Update citation information CITATION.cff and BibTeX at https://github.com/GenericMappingTools/pygmt#citing-pygmt
  • Update authorship list if necessary
  • Update CITATION.cff
    • Update DOI
    • Update date released
    • Update version
  • Update BibTeX in README
    • Update the BibTeX key
    • Update date released
    • Update version
    • Update DOI and URL
• Copy the draft release note from https://github.com/GenericMappingTools/pygmt/releases to doc/changes.md
• Edit the changelog to look nice (see maintainers guide for details)
  • Add the separator --- between the old and new changelog sections
  • Update the release date and the DOI badge in doc/changes.md
  • Edit the list of people who contributed to the release, linking to their GitHub account. Sort their names by the number of commits made since the last release. Use the following command:

    git shortlog v0.17.0..HEAD -sne --group=author --group=trailer:co-authored-by
    

  • Edit the change list to remove any trivial changes (updates to the README, typo fixes, CI configuration, etc)
  • Update with any remaining PRs merged before release
  • Add highlights