Changelog entry for v0.7.0

[seisman]

Description of proposed changes

This PR adds changelog entry for v0.7.0.

Preview:

Previous release at #1874.

Changelog made by following the instructions at https://github.com/GenericMappingTools/pygmt/blob/main/doc/maintenance.md#updating-the-changelog

TODO:

• Copy the draft release note from https://github.com/GenericMappingTools/pygmt/releases to doc/changes.md
• Update the DOI badge
• Update citation information https://github.com/GenericMappingTools/pygmt#citing-pygmt and CITATION.cff
• Add the version to the compatibility table https://github.com/GenericMappingTools/pygmt#compatibility-with-gmtpythonnumpy-versions
• Add highlights
• Update with any remaining PRs merged before release
• Edit the change list to remove any trivial changes (updates to the README, typo fixes, CI configuration, etc)
• 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 (e.g., use git shortlog HEAD...v0.1.2 -sne).

Relates to #1966

[weiji14]

Need to add @yvonnefroehlich and @andrebelem's names to CITATION.cff too

[seisman]

Need to add @yvonnefroehlich and @andrebelem's names to CITATION.cff too

I've added @yvonnefroehlich and @andrebelem to CITATION.cff (14e4d90). The order are based on the number of commits listed in this page (https://github.com/GenericMappingTools/pygmt/graphs/contributors).

[weiji14]

Other than Max's suggested changes, looks good to me! Thanks again @seisman for handling the changelog and the release!

[weiji14]

Forgot to add Andre and Yvonne's names to the BibTeX 😅