Returns if the given NPC class name is an enemy. Returns true if the entity name is one of the following:

• monster_alien_grunt
• monster_nihilanth
• monster_tentacle
• monster_alien_slave
• monster_bigmomma
• monster_bullchicken
• monster_gargantua
• monster_human_assassin
• monster_babycrab
• monster_human_grunt
• monster_cockroach
• monster_houndeye
• monster_zombie
• monster_headcrab
• monster_alien_controller
• monster_turret
• monster_miniturret
• monster_sentry
• npc_antlion
• npc_antlionguard
• npc_antlionguardian
• npc_barnacle
• npc_breen
• npc_clawscanner
• npc_combine_s
• npc_cscanner
• npc_fastzombie
• npc_fastzombie_torso
• npc_headcrab
• npc_headcrab_fast
• npc_headcrab_poison
• npc_hunter
• npc_metropolice
• npc_manhack
• npc_poisonzombie
• npc_strider
• npc_stalker
• npc_zombie
• npc_zombie_torso
• npc_zombine
• npc_combine_camera
• npc_turret_ceiling
• npc_combinedropship
• npc_combinegunship
• npc_helicopter
• npc_turret_floor
• npc_antlion_worker
• npc_headcrab_black