dissimilarity.py missing from methods folder

[FanwangM]

Discussed in https://github.com/theochem/Selector/discussions/207

^{Originally posted by **JackyZzZz** May 15, 2024} I noticed that we need to import ```dissimilarity.py``` from ```methods``` in the ```Running Dissimilarity Algorithms``` example in the documentation. However, it seems like this file is missing from the methods folder. P.S: I think it is renamed to distance.py, so we should probably update the documentation. ## Add-on: - the first parameter of ```select``` function in base.py is ```X```, not ```arr``` in the documentation

I will do a cleaning up before more actual code changes.

[FanwangM]

This is suppressd by https://github.com/theochem/Selector/issues/216.