Prevents players of the same team shooting eachother.
Put teams into your server's client_packages directory, then add require('teams'); to client_packages/index.js.
It's pretty simple, just set currentTeam shared variable of a player like this:
// both strings and numbers should work
playerEntity.data.currentTeam = whatever;
And set currentTeam to null if you want to reset someone's team.
This resource doesn't prevent all kinds of friendly fire, for example projectile weapons like RPG can hurt teammates, you can still run teammates over with a vehicle etc. You can check if both killer and victim is on the same team and punish the killer, though.