[Suggestion] Add type hints

[riiswa]

I think adding type hinting can improve the overall quality of rlberry, but it will be a huge work. What do you think ?

[TimotheeMathieu]

I think this is a good idea and we don't have to do everything at once, we could do something gradual

• Do a PR that add type hint to the principal algorithms of rlberry (AgentManager, plot and eval functions, Base classes like Model and AgentWithSimplePolicy...).
• Use typing in the new PR
• Do other PR to step by step have it in all rlberry

On the other hand, I think for now improving the documentation should come first (in particular issue #188 and add some tutorials to populate the user guide), but this is just my opinion. We can keep this issue for later maybe.

[riiswa]

Duplicated from #15