Add EditorContext, refactor utils, add system managers

src/app/editor/system/resource_manager.h

@@ -0,0 +1,30 @@
+#ifndef YAZE_APP_EDITOR_SYSTEM_RESOURCE_MANAGER_H
+#define YAZE_APP_EDITOR_SYSTEM_RESOURCE_MANAGER_H
+
+#include <cstddef>
+
+namespace yaze {
+namespace app {
+namespace editor {
+
+// System resource manager.
+class ResourceManager {
+ public:
+  ResourceManager();
+  ~ResourceManager();
+
+  void Load(const char* path);
+  void Unload(const char* path);
+  void UnloadAll();
+
+  size_t Count() const;
+
+ private:
+  size_t count_;
+};
+
+} // namespace editor
+} // namespace app
+} // namespace yaze
+
+#endif // YAZE_APP_EDITOR_SYSTEM_RESOURCE_MANAGER_H