Add Tutorial "Projection approaches for Optimal Transport"

[vmart20]

Project for OT-ENSAE 2023.

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[vmart20]

I've added new words ("mathbb" and "rightarrow") in docs/spelling/latex.txt to ignore spelling warnings in latex.

[michalk8]

I've added new words ("mathbb" and "rightarrow") in docs/spelling/latex.txt to ignore spelling warnings in latex.

These need not be added, if you look at https://ott-jax--368.org.readthedocs.build/en/368/tutorials/notebooks/projection_approaches.html, the equation doesn't render properly.

[vmart20]

The lint error is because of this:
/home/runner/work/ott/ott/docs/_autosummary/ott.tools.gaussian_mixture.gaussian.Gaussian.from_samples.rst:3: WARNING: broken link: https://www.gnu.org/software/gsl/doc/html/statistics.html#weighted-samples

This is not related to this commit and the website is up now.