updated readme to mention verilator dependency (#1984)

* added to readme

* Update README.md

Co-authored-by: Jack Koenig <jack.koenig3@gmail.com>

Co-authored-by: Jack Koenig <jack.koenig3@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>