Lemons should be added to Minecraft. They can only grow on mangrove roots in the mangrove biome, and crafting 1 lemon gives you 4 seeds. You can plant them by placing the seed below the mangrove root. They should replenish no more than 1 & 1/2 hunger bars. They can be bone mealed. If a wandering trader were to sell them, it should cost no more than 2 emeralds per lemon seed. Lemons could also be used to make lemonade, which heals 5 hunger bars, by combining sugar, a water bottle, a honey bottle, and 3 lemons. The way you craft it is completely in Minecraft's hands.