Add selenium related requirements to requirements.txt

[sigmaeni]

Notably, webdriver-manager and selenium-stealth seem to be required for genesis to perform selenium searches (when looking up APIs, etc.). Adding these to requirements.txt eliminates the errors encountered when using the genesis jupyter notebook.

[VRSEN]

Hey @sigmaeni, these are only used for the browsing agent, so I don't want the whole project to depend on them. Maybe we can add some checks and more descriptive error messages when initializing the browsing agent. The jupyter notebook has pip install on top