General Doc refresher

[MMathisLab]

• small changes to home/landing page
• changed ref. of figures to 2023
• added ref to 2025 paper

[stes]

lgtm

[MMathisLab]

note; test failing; need to investigate in usage.rst

1274      # 8. Adapt the model to a new session
1275      cebra_model.fit(new_neural_data, adapt = True)
12[76](https://github.com/AdaptiveMotorControlLab/CEBRA/actions/runs/13618482342/job/38064623999?pr=232#step:11:77) 
1277      # 9. Decode discrete labels behavior from the embedding
1278      decoder = cebra.KNNDecoder()
1279      decoder.fit(train_embedding, train_discrete_label)
1280      prediction = decoder.predict(valid_embedding)
1281      assert prediction.shape == (30,)
12[82](https://github.com/AdaptiveMotorControlLab/CEBRA/actions/runs/13618482342/job/38064623999?pr=232#step:11:83) 
UNEXPECTED EXCEPTION: AttributeError("'numpy.ndarray' object has no attribute 'continuous_index'")
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.10.16/x64/lib/python3.10/site-packages/pytest_sphinx.py", line 421, in _DocTestRunner__run
    exec(
  File "<doctest usage.rst[37]>", line 44, in <module>
AttributeError: 'numpy.ndarray' object has no attribute 'continuous_index'
usage.rst:1282: UnexpectedException