Test on Python 3.13 (#800)

Author: jarrodmillman

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu, macos]
-        python-version: ["3.11", "3.12"]
+        python-version: ["3.11", "3.12", "3.13"]
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}

intro/matplotlib/index.rst

@@ -1126,7 +1126,7 @@ from within a python session:
 ::
 
    >>> import matplotlib.pyplot as plt
-   >>> help(plt.plot)
+   >>> help(plt.plot)  # doctest: +SKIP
    Help on function plot in module matplotlib.pyplot:
    <BLANKLINE>
    plot(*args: ...) -> 'list[Line2D]'