Add optional dependencies to pyproject.toml

[seisman]

Description of proposed changes

As suggested in #1848 (comment), this PR adds optional-dependencies to pyproject.toml so that people can run pip install pygmt[all] to install pygmt with optional dependencies included.

To test it locally, you can check out this branch, change into the root directory, and run

pip install .

and

pip install .[all]

you should see that pip install .[all] also check if geopandas is installed while pip install . doesn't.

Address #1848 (comment).

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

[seisman]

I'm not sure if we should update the pip install pygmt command to pip install pygmt[all]
in the installation instructions (https://www.pygmt.org/dev/install.html).

[weiji14]

I'm not sure if we should update the pip install pygmt command to pip install pygmt[all] in the installation instructions (https://www.pygmt.org/dev/install.html).

Wouldn't recommend replacing it with pip install pygmt[all], but I think we can mention the pip install pygmt[all] command in https://www.pygmt.org/v0.7.0/install.html#using-pip and indicate that this will install optional dependencies like geopandas.

[weiji14]

Should we add ipython as well as mentioned in https://www.pygmt.org/v0.7.0/install.html#dependencies?

Suggested change

	"geopandas"
	"geopandas",
	"ipython"

[seisman]

Yes, because we also try to import IPython in our codes.