FeynGrav 4.0

We present the new version of FeynGrav, a package that provides tools for working with Feynman rules for gravity models. The new version addresses two principal issues and improves the user experience. Firstly, we present a more sophisticated implementation of the BRST formalism for general relativity and quadratic gravity, producing a finite set of interaction rules between ghosts and gravitons. We also implement a higher-derivative gauge-fixing term for quadratic gravity. Secondly, we implement Feynman rules for Cheung-Remmen variables. These variables present the general relativity action in a polynomial form and produce a finite set of Feynman rules. Lastly, we introduce minor quality-of-life improvements to the package to enhance the user experience.