Add van Hove function tutorials

[ChiCheng45]

Added tutorial 2 which goes through some background on the van Hove function and a step-by-step guide on calculating the van Hove function with MDANSE using a liquid argon trajectory.

Clean up some more files that were missed in #12.

Updated the conversion script in tutorial 1 so that it works with the new chunking change. Adjusted the tutorial 1 figures so that they have a smaller width and are centered to enhance readability.

@MBartkowiakSTFC feel free to make any typo fixes/changes etc.

[ChiCheng45]

@MBartkowiakSTFC I'm unable to push to my branch for some reason I think you need to update the rules.

remote: error: GH013: Repository rule violations found for refs/heads/chi/tutorial-van-hove.
remote: Review all repository rules at https://github.com/ISISNeutronMuon/MDANSE-Examples/rules?ref=refs%2Fheads%2Fchi%2Ftutorial-van-hove
remote:
remote: - Changes must be made through a pull request.
remote:
To https://github.com/ISISNeutronMuon/MDANSE-Examples.git
 ! [remote rejected] chi/tutorial-van-hove -> chi/tutorial-van-hove (push declined due to repository rule violations)
error: failed to push some refs to 'https://github.com/ISISNeutronMuon/MDANSE-Examples.git'