Datapack to add heart

I've been trying to add a craftable heart to an already existing lifesteal datapack, but i can't get it to work. Does anyone know how to program a datapack to give a player a heart if they right click a heart after having crafted one. I already have the "recipes" folder setup. this is the datapack im trying to implement my code/functions in.

https://modrinth.com/datapack/lifesteal-datapack

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