POC: Add Figure.scatter

[seisman]

Description of proposed changes

Reference: Matplotlib.pyplot.scatter

Example:

import pygmt

x = [-4, -2, 0, 2, 4]

fig = pygmt.Figure()
fig.basemap(region=[-5, 5, -3, 3], projection="X10c/4c", frame=True)

fig.scatter(x=x, y=[-2] * 5, symbol="c", size="0.5c", fill="gray", pen="1p,orange")

fig.scatter(x=x, y=[-1] * 5, symbol=["c", "i", "t", "a", "d"], size="0.5c", fill="gray", pen="1p,orange")

fig.scatter(x=x, y=[0] * 5, symbol="c", size=[0.2, 0.5, 1.0, 0.2, 0.4], fill="gray", pen="1p,orange")

fig.scatter(x=x, y=[1] * 5, symbol=["c", "i", "t", "a", "d"], size=[0.2, 0.5, 1.0, 0.2, 0.4], fill="gray", pen="1p,orange")

fig.show()

Fixes #

Preview: https://pygmt-dev--3602.org.readthedocs.build/en/3602/api/generated/pygmt.Figure.scatter.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.
• Use underscores (not hyphens) in names of Python files and directories.

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