Refactored libimhex to and includes to better represent it as library

plugins/libimhex/include/hex/api/event.hpp

@@ -0,0 +1,46 @@
+#pragma once
+
+#include <hex.hpp>
+
+#include <vector>
+#include <functional>
+
+namespace hex {
+
+    enum class Events : u32 {
+        FileLoaded,
+        DataChanged,
+        PatternChanged,
+        FileDropped,
+        WindowClosing,
+        RegionSelected,
+
+        SelectionChangeRequest,
+
+        AddBookmark,
+        AppendPatternLanguageCode,
+
+        ProjectFileStore,
+        ProjectFileLoad,
+
+        SettingsChanged,
+
+
+        /* This is not a real event but a flag to show all events after this one are plugin ones */
+        Events_BuiltinEnd
+    };
+
+    struct EventHandler {
+        void *owner;
+        Events eventType;
+        std::function<void(const void*)> callback;
+    };
+
+    class EventManager {
+    public:
+        static void post(Events eventType, const void *userData);
+        static void subscribe(Events eventType, void *owner, std::function<void(const void*)> callback);
+        static void unsubscribe(Events eventType, void *sender);
+    };
+
+}