Add a gallery example showing the usage of Figure.hlines and Figure.vlines

[michaelgrund]

Description of proposed changes

This PR adds a gallery example to show how the Figure.hlines and Figure.vlines methods can be used.

Related to #923 and #3726

Preview: https://pygmt-dev--3755.org.readthedocs.build/en/3755/gallery/lines/hlines_vlines.html#

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 command is:

• /format: automatically format and lint the code

[michaelgrund]

/format

[michaelgrund]

/format

[michaelgrund]

/format

[seisman]

Please ignore the failing "Style Checks", which will be addressed in #3763.

[seisman]

@michaelgrund Thanks for making the gallery example! I feel it's already in great shape!

My last comment is about the figure title. Currently we use hlines/vlines Cartesian/polar/geographic. Maybe Cartesian/Polar/Geographic hlines/vlines are better?