Better Spawner/Rarity Multiplier

A rarity multiplier is a component of a SpawnInfo which lets its rarity change based on particular conditions or anticonditions.

The properties of a rarity multiplier are as follows:

Property label	Type of value	Description
"multiplier"	A decimal number	The number to multiply the rarity by.
"condition"	An optional Better_Spawner/Spawn_Condition.	The condition that must be passed to apply this multiplier. This may be left out if an anticondition is given.
"anticondition"	An optional Better_Spawner/Spawn_Condition.	The anticondition that must fail to apply this multiplier. This may be left out if a condition is given.

An entity that spawns 3x more often when it is raining or storming (so when it isn't clear weather) in a Deep Ocean biome might have the following rarity multiplier:

    {
        "multiplier": 3.0,
        "condition": {
            "stringBiomes": [
                "deep_ocean"
            ]
        },
        "anticondition": {
	    "weathers": [
                "CLEAR"
            ]
	}
    }