build: Refactor ImHexAPI into multiple separate files

lib/libimhex/include/hex/api/imhex_api/messaging.hpp

@@ -0,0 +1,33 @@
+#pragma once
+
+#include <hex.hpp>
+
+#include <functional>
+#include <string>
+#include <map>
+#include <vector>
+
+EXPORT_MODULE namespace hex {
+
+    /**
+     * Cross-instance messaging system
+     * This allows you to send messages to the "main" instance of ImHex running, from any other instance
+     */
+    namespace ImHexApi::Messaging {
+
+        namespace impl {
+
+            using MessagingHandler = std::function<void(const std::vector<u8> &)>;
+
+            const std::map<std::string, MessagingHandler>& getHandlers();
+            void runHandler(const std::string &eventName, const std::vector<u8> &args);
+
+        }
+
+        /**
+         * @brief Register the handler for this specific event name
+         */
+        void registerHandler(const std::string &eventName, const impl::MessagingHandler &handler);
+    }
+
+}