WIP: Add inline example for pygmt.datasets.list_sample_data

[maxrjones]

Description of proposed changes

This PR adds an inline example for pygmt.datasets.list_sample_data. It is a possible solution to https://github.com/GenericMappingTools/pygmt/issues/1774 and would be easier to maintain than table/list in the docstring since the output from the example could be easily updated.

It is listed as WIP because the style checks fail with line-too-long errors.

Addresses #1774

Reminders

• [ ] Run make format and make check to make sure the code follows the style guide.
• [ ] Add tests for new features or tests that would have caught the bug that you're fixing.
• [ ] Add new public functions/methods/classes to doc/api/index.rst.
• [ ] Write detailed docstrings for all functions/methods.
• [ ] If wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• [ ] If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

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

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version