Add scikit-learn to the example gallery (#1985)

Thanks for the amazing theme! Scikit-learn has migrated to
pydata-sphinx-theme for the main website since version 1.5
(scikit-learn/scikit-learn#29038), and the nice
three-column layout has unlocked many potential improvements to our
website UI/UX-wise. This PRs adds scikit-learn to the list of `Other
projects using this theme`.

However though scikit-learn is not one of the earliest adopters of
pydata-sphinx-theme, I'm asking if it can fit into the list of `Featured
projects` as we have many quite some customizations that could be
helpful for other users of the theme. Some of them include:

- [Landing page](https://scikit-learn.org/)
- [API references](https://scikit-learn.org/stable/api/index.html) (a
searchable table on the index page containing all APIs while keeping the
hierarchy in the primary sidebar)
- [Each API
page](https://scikit-learn.org/stable/modules/generated/sklearn.linear_model.LogisticRegression.html)
(customizing the secondary sidebar)
- [Gallery
examples](https://scikit-learn.org/stable/auto_examples/release_highlights/plot_release_highlights_1_5_0.html)
(secondary sidebar customization with sphinx-gallery)
- [Platform-specific installation
instructions](https://scikit-learn.org/stable/install.html#installing-the-latest-release)
(CSS customizations based on tabs in sphinx-design)
-
[Dropdowns](https://scikit-learn.org/stable/modules/linear_model.html#references)
(anchor link for dropdown blocks; toggle-all button for Ctrl-F
searching)
- Algolia search (WIP):
scikit-learn/scikit-learn#29666
- Many other CSS customizations

Looking forward to your feedback :)

*BTW some of the projects were not placed in alphabetical order as
required so I reordered a bit.*

docs/_static/gallery.yaml

@@ -49,6 +49,10 @@
   link-alt: SciPy docs
   link: https://docs.scipy.org/doc/scipy/
   img-bottom: ../_static/gallery/scipy.png
+- title: scikit-learn
+  link-alt: scikit-learn docs
+  link: https://scikit-learn.org/
+  img-bottom: ../_static/gallery/scikit-learn.png
 - title: SEPAL
   link-alt: SEPAL docs
   link: https://docs.sepal.io/en/latest/index.html

docs/examples/gallery.md

@@ -32,6 +32,9 @@ Thanks for your support!
 - title: CuPy
   link-alt: CuPy docs
   link: https://docs.cupy.dev/en/stable/index.html
+- title: DecentralChain
+  link-alt: DecentralChain docs
+  link: https://docs.decentralchain.io/en/master/
 - title: Fairlearn
   link-alt: Fairlearn docs
   link: https://fairlearn.org/main/about/
@@ -44,16 +47,13 @@ Thanks for your support!
 - title: MegEngine
   link-alt: MegEngine docs
   link: https://www.megengine.org.cn/doc/stable/en/index.html
+- title: Pastas
+  link-alt: Pastas docs
+  link: https://pastas.readthedocs.io/
 - title: PhaseFieldX
   link-alt: PhaseFieldX docs
   link: https://phasefieldx.readthedocs.io/en/latest/index.html
 - title: PyVista
   link-alt: PyVista docs
   link: https://docs.pyvista.org
-- title: Pastas
-  link-alt: Pastas docs
-  link: https://pastas.readthedocs.io/
-- title: DecentralChain
-  link-alt: DecentralChain docs
-  link: https://docs.decentralchain.io/en/master/
 ```

tests/warning_list.txt

@@ -10,6 +10,7 @@ WARNING: image file not readable: _static/gallery/arviz.png
 WARNING: image file not readable: _static/gallery/sepal.png
 WARNING: image file not readable: _static/gallery/matplotlib.png
 WARNING: image file not readable: _static/gallery/brightway.png
+WARNING: image file not readable: _static/gallery/scikit-learn.png
 WARNING: autosummary: stub file not found 'urllib.parse.DefragResult.count'. Check your autosummary_generate setting.
 WARNING: autosummary: stub file not found 'urllib.parse.DefragResult.index'. Check your autosummary_generate setting.
 WARNING: autosummary: stub file not found 'urllib.parse.DefragResultBytes.count'. Check your autosummary_generate setting.