sys: Merge splash screen and ImHex into one application

This fixes so many issues the previous implementation had, especially on Unix

include/init/splash_window.hpp

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <functional>
+#include <future>
+#include <vector>
+
+#include <mutex>
+
+struct GLFWwindow;
+
+namespace hex::init {
+
+    class WindowSplash {
+    public:
+        WindowSplash(int &argc, char **&argv);
+        ~WindowSplash();
+
+        bool loop();
+
+        void addStartupTask(std::string_view taskName, const std::function<bool()> &task) {
+            this->m_tasks.emplace_back(taskName, task);
+        }
+
+    private:
+        GLFWwindow *m_window;
+        std::mutex m_progressMutex;
+        float m_progress = 0;
+        std::string m_currTaskName;
+
+        void initGLFW();
+        void initImGui();
+
+        void deinitGLFW();
+        void deinitImGui();
+
+        std::future<bool> processTasksAsync();
+
+        std::vector<std::pair<std::string, std::function<bool()>>> m_tasks;
+    };
+
+}