Add support for custom providers via plugins

plugins/libimhex/include/plugin.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <glad/glad.h>
+#include <imgui.h>
+
+#include <hex.hpp>
+#include <views/view.hpp>
+#include <providers/provider.hpp>
+
+#define IMHEX_PLUGIN    namespace hex::plugin::internal {                                               \
+                            void initializePlugin(ImGuiContext *ctx, hex::prv::Provider **provider) {   \
+                                if (glGetString == NULL)                                                \
+                                    gladLoadGL();                                                       \
+                                ImGui::SetCurrentContext(ctx);                                          \
+                                hex::prv::Provider::setProviderStorage(*provider);                      \
+                            }                                                                           \
+                        }                                                                               \
+                        namespace hex::plugin