New flag mob-spawning-spawner

[matix931]

Is your feature request related to a problem? Please describe. I have a lot of plots for players protected by WorldGuard and supported by AdvancedRegionMarket. Mob spawning is disabled, but i want to allow players to spawn mobs from spawners.

Describe the solution you'd like Flag mob-spawning-spawner should have priority over mob-spawning. When i set mob-spawning-spawner to true, and mob-spawning to deny. Then mobs should spawn only from spawners.

Describe alternatives you've considered Enabling all monsters on region...

Additional context