Add `add_animation` input sources to use instead `event ***`

[Petr Ohlídal]

From Discord https://discord.com/channels/136544456244461568/189904947649708032/1081269810769440888

I have animations that trigger when X is pressed. The animations I have set are in their “disabled” state when spawned. The animations work fine for anybody who has spawn engine running turned off, because you spawn and start the actor therefor triggering the animation. But if somebody were to have engines spawn running turned on, then the actor would spawn already started but the animations are still in their disabled state, therefor reversing the function of the animation.