Support for finding the previous evolution step of a Pokemon.

src/Library/Species/SpeciesLibrary.cpp

@@ -1 +1,20 @@
 #include "SpeciesLibrary.hpp"
+namespace PkmnLib::Library {
+    ArbUt::BorrowedPtr<const PokemonSpecies>
+    SpeciesLibrary::FindPreEvolution(const ArbUt::BorrowedPtr<const PokemonSpecies>& species) const noexcept {
+        if (_preEvolutionCache.Has(species)) {
+            return _preEvolutionCache[species];
+        }
+        for (auto& s : _values) {
+            auto pkmn = (PokemonSpecies*)s.second.get();
+            for (auto& evo : pkmn->GetEvolutions()) {
+                if (evo->GetNewSpecies() == species) {
+                    auto non_const = const_cast<SpeciesLibrary*>(this);
+                    non_const->_preEvolutionCache[species] = pkmn;
+                    return pkmn;
+                }
+            }
+        }
+        return nullptr;
+    }
+}