docs: improvements to self-signed certificates docs

@lx_brz suggested to clarify the limitations of self-signed certificates. This will prevent confusion for people who'd try to use self-singed certificates and HTTPS proxy at the same time (#314)

I also:

• removed unused enableExperimentalFeatures setting
• moved reviewer setting to custom queries (leaving it in the main settings section was a mistake we made when refactoring custom queries documentation: docs: separate custom query documentation into a new file)

Related to #314