Release/v0.5.1

[weidel-p]

This PR updates the website to document Lava version 0.5.1 and the corresponding libraries.

Still left to do:

• Fix formatting issues in lava-optimization. (lava-optimization/src/lava/lib/optimization/solvers/bayesian/solver.py and lava-optimization/src/lava/lib/optimization/solvers/bayesian/solver.py have faulty docstrings)
• Check if the 'getting started' section is up to date with the current state of the libraries

[bamsumit]

I have noticed two things for now:

• 
  I would suggest red portion to be collapsed as I would expect to get a summary/table of content of the modules here and this gets distracting
• 
  Latex rendering is broken. This is probably in your setup because I noticed this in your earlier renderings.

[weidel-p]

I changed the max-depth level to two to comply with @bamsumit request. I also think it's nicer like that. I also added the changes in the current lava-optimization PRs.

The equations will be rendered correctly in CI, just not on the machine I used for preview.

[bamsumit]

I changed the max-depth level to two to comply with @bamsumit request. I also think it's nicer like that. I also added the changes in the current lava-optimization PRs.

The equations will be rendered correctly in CI, just not on the machine I used for preview.

I think there is one more level that needs change in max-depth level:

Looks like that's only for lava-dl

[weidel-p]

Oh, sorry, I somehow thought that lava-dl was already formatted correctly. I now reduced the max-depth there, too.

[bamsumit]

Looks good not Philipp. Thanks :)