Add check for "unknown" parameters in DocSearch config

[JanPetr]

I had a min_indexed_lvl parameter in a config, but the parameter is actually called min_indexed_level. But DocSearch scraper crawled the site as usual and I had no idea there is something wrong.

Is it possible to add a check which would raise a warning message when there are “unknown” parameters in the config?

[ElPicador]

Yeah you are right, I had the same issue :/

We have some validations: https://github.com/algolia/docsearch-scraper/blob/master/scraper/src/config/config_validator.py

It should be pretty easy to had more validations.