Suggest recommending PostgreSQL Row Level Security in the README

Many people likely use PostgreSQL’s Row Level Security together with this gem as part of a defense-in-depth strategy. Don’t you think the README should recommend using PostgreSQL Row Level Security as well?

Start by reading the README and locating the section that explains tenant isolation or security for this gem. Add a recommendation to use PostgreSQL Row Level Security as defense in depth, then verify that the README clearly explains the recommendation without implying it is required.

Written by the indexing model from the issue text.