DOC: Technical Reference: Add table for text formatting

[yvonnefroehlich]

Description of proposed changes

Following https://docs.generic-mapping-tools.org/dev/text.html#description, this PR addes a table to the Technical References for formatting text.

Preview: https://pygmt-dev--3976.org.readthedocs.build/en/3976/techref/text_formatting.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

[yvonnefroehlich]

A new ruff version (0.12.0) was released a few hours ago (https://pypi.org/project/ruff/) leading to several (~20) failing Style checks (https://github.com/GenericMappingTools/pygmt/actions/runs/15714747994/job/44281566411?pr=3976).

[seisman]

A new ruff version (0.12.0) was released a few hours ago (https://pypi.org/project/ruff/) leading to several (~20) failing Style checks (https://github.com/GenericMappingTools/pygmt/actions/runs/15714747994/job/44281566411?pr=3976).

Yes, addressed in #3980.

[seisman]

Perhaps we should also update https://www.pygmt.org/dev/tutorials/basics/text.html, maybe in a separate PR?

[yvonnefroehlich]

Perhaps we should also update https://www.pygmt.org/dev/tutorials/basics/text.html, maybe in a separate PR?

Good point! Adding a section to this tutorial sounds good to me, or do we just want to add a link to this Technical Reference page?

[seisman]

Maybe a separate tutorial or gallery example is better?

[seisman]

Suggested change

	The table below shows how text added to a plot as well as the title of the plot and
	labels of colorbars, Cartesian axes, and legend entries can be formatted. Changing
	The table below shows how text added to a plot, such as text strings added via `Figure.text`, plot title, labels of Cartesian axes and colorbars, and legend entries.
	Changing