add safehaven-4.0.0-release.md
add safehaven-4.0.0-release.md

StephanieWong/PublicKB,mfar78/PublicKB,anthonyvetter/PublicKB,daveshac/PublicKB,jtowns3/PublicKB,jwebs1/PublicKB,ack/PublicKB,robertlesieur/PublicKB,robcaldwell/PublicKB,jwcolbert/PublicKB,DLM1/PublicKB