[WIP] Add CAN Method

[YanisLalou]

Paper: https://arxiv.org/pdf/1901.00976 Mostly eq 3-4-5 + paragraph 3.4

New Features:

• CAN and CANLoss Implementation:
  • Added CANLoss class to skada/deep/_divergence.py to implement the contrastive domain discrepancy (CDD) loss.
  • Added CAN function to skada/deep/_divergence.py to implement the CAN domain adaptation method.

New Utilities:

• SphericalKMeans:
  • Added SphericalKMeans class to skada/deep/utils.py for clustering using cosine similarity.

Testing:

• New Tests for CAN:
  • Added tests for CAN in test_deep_divergence.py to ensure the new method works as expected.

Still needs to be done:

• Double check the implementation