Create EditorHelpHighlighter in Project Manager

so that it works in Editor Settings opened without loading a project.

(cherry picked from commit 86d336e1e0e32f61c457291351bb9b7e7c2c66c1)

editor/project_manager/project_manager.cpp

@@ -38,6 +38,7 @@
 #include "core/os/os.h"
 #include "core/version.h"
 #include "editor/asset_library/asset_library_editor_plugin.h"
+#include "editor/doc/editor_help.h"
 #include "editor/editor_string_names.h"
 #include "editor/gui/editor_about.h"
 #include "editor/gui/editor_file_dialog.h"
@@ -75,6 +76,8 @@
 #include "servers/physics_3d/physics_server_3d.h"
 #endif // PHYSICS_3D_DISABLED
 
+#include "modules/modules_enabled.gen.h" // For gdscript, mono. (For editor help highlighter).
+
 constexpr int GODOT4_CONFIG_VERSION = 5;
 
 ProjectManager *ProjectManager::singleton = nullptr;
@@ -1383,6 +1386,10 @@ ProjectManager::ProjectManager() {
 		OS::get_singleton()->set_low_processor_usage_mode(true);
 	}
 
+#if defined(MODULE_GDSCRIPT_ENABLED) || defined(MODULE_MONO_ENABLED)
+	EditorHelpHighlighter::create_singleton();
+#endif
+
 	SceneTree::get_singleton()->get_root()->connect("files_dropped", callable_mp(this, &ProjectManager::_files_dropped));
 
 	// Initialize UI.
@@ -1970,6 +1977,11 @@ ProjectManager::ProjectManager() {
 ProjectManager::~ProjectManager() {
 	singleton = nullptr;
 	EditorInspector::cleanup_plugins();
+
+#if defined(MODULE_GDSCRIPT_ENABLED) || defined(MODULE_MONO_ENABLED)
+	EditorHelpHighlighter::free_singleton();
+#endif
+
 	if (EditorSettings::get_singleton()) {
 		EditorSettings::destroy();
 	}