Implements TryGet functions on several libraries.

src/Library/ItemLibrary.cpp

@@ -1,5 +1,16 @@
 #include "ItemLibrary.hpp"
 
+bool CreatureLib::Library::ItemLibrary::TryGetItem(const std::string& name,
+                                                   const CreatureLib::Library::Item*& item) const {
+    auto find = this->_items.find(name);
+    if (find == this->_items.end()) {
+        item = nullptr;
+        return false;
+    }
+    item = find->second;
+    return true;
+}
+
 const CreatureLib::Library::Item* CreatureLib::Library::ItemLibrary::GetItem(const std::string& name) const {
     return this->_items.at(name);
 }