feat: Display detailed error message when loading of project fails (#1135)

In order to do this I add to make some other additions :
- Add a warning popup (TODO, maybe add some icons to differentiate
error/warning popups in a future PR ?)
- create showError() and showWarning() functions, as helpers to show a
message both to the logs and as a popup

plugins/builtin/source/plugin_builtin.cpp

@@ -31,6 +31,7 @@ namespace hex::plugin::builtin {
     void registerBackgroundServices();
     void registerNetworkEndpoints();
     void registerFileHandlers();
+    void registerProjectHandlers();
 
     void addFooterItems();
     void addTitleBarButtons();
@@ -71,6 +72,7 @@ IMHEX_PLUGIN_SETUP("Built-in", "WerWolv", "Default ImHex functionality") {
     registerBackgroundServices();
     registerNetworkEndpoints();
     registerFileHandlers();
+    registerProjectHandlers();
 
     addFooterItems();
     addTitleBarButtons();