Adds function to set IsEgg on Pokemon

src/Battling/Pokemon/Pokemon.hpp

@@ -62,6 +62,7 @@ namespace PkmnLib::Battling {
             return _effortValues.SetStat(stat, value);
         }
         inline bool IsEgg() const noexcept { return _isEgg; }
+        inline void SetIsEgg(bool value) noexcept { _isEgg = value; }
 
         inline ArbUt::BorrowedPtr<const PkmnLib::Library::PokemonSpecies> GetPokemonSpecies() const noexcept {
             return _species.As<const PkmnLib::Library::PokemonSpecies>();