[Suggestion] Add support for Mythicmobs

[LeafletXD]

Allow the Mythicmobs entities to be calculated as valid entities in the format mythicmob: [custom mob name] Here is the example config:

type: killentity
value: mythicmobs: soldier
amount: 10

or

type: killentity
value: mm_soldier
amount: 10

Mythicmobs: https://www.spigotmc.org/resources/%E2%9A%94-mythicmobs-free-version-%E2%96%BAthe-1-custom-mob-creator%E2%97%84.5702/

I know someone has already put forward this suggestion, but I still want to make it, please :(

[LeafletXD]

Or

type: killentity
value: 
mm: soldier // Can be added by oneself
amount: 10