Will pass if the game is in this difficulty. Known values are 'peaceful', 'easy', 'normal', 'hard', and 'hardcore'. You can also check the additional difficulty based on area (the 'regional difficulty' https://minecraft.gamepedia.com/Difficulty#Regional_difficulty). For the regional difficulty, you can use both min and max, or leave one out.

Example Usage: (applies if the difficulty is peaceful)

"conditions": [
	{
		"condition": "lootoverhaul:difficulty",
		"difficulty": "peaceful"
	}
]

Or: (applies if the difficulty is greater than easy)

"conditions": [
	{
		"condition": "lootoverhaul:difficulty",
		"difficulty": [
			"normal",
			"hard",
			"hardcore"
		]
	}
]

Or: (checks for regional difficulty of at least 2)

"conditions": [
	{
		"condition": "lootoverhaul:difficulty",
		"regional": {
			"min": 2.0
		}
	}
]