function getEnv(slots, envId) {
	return (
		(slots.lastConfigArray &&
			slots.lastConfigArray.pluginEnvironments.get(envId)) ||
		BuiltInEnvironments.get(envId) ||
		null
	);
}
Get an environment.
@param {LinterInternalSlots} slots The internal slots of Linter.
@param {string} envId The environment ID to get.
@returns {Environment|null} The environment.