### Godot version

Godot 4.0.3

### System information

Windows 10 64 bits NVIDIA GeForce GTX 1060

### Issue description

Ctrl+K is a shortcut normally used to comment out the current line. It works in the shader editor, but for some reason, it doesn't if your shader has the `.gdshaderinc` extension (aka it's a shader include). Shader Includes are the same language, we should be able to use that feature.

### Steps to reproduce

Create a `.gdshaderinc` file. Write some code in it. Observe you can't use Ctrl+K to comment out lines.

### Minimal reproduction project

[CommentLinesShaderInc.zip](https://github.com/godotengine/godot/files/11739881/CommentLinesShaderInc.zip)

case BOOKMARK_GOTO_NEXT: {
			shader_editor->goto_next_bookmark();
		} break;
		case BOOKMARK_GOTO_PREV: {
			shader_editor->goto_prev_bookmark();
		} break;
		case BOOKMARK_REMOVE_ALL: {
			shader_editor->remove_all_bookmarks();
		} break;
		case HELP_DOCS: {
			OS::get_singleton()->shell_open(vformat("%s/tutorials/shaders/shader_reference/index.html", VERSION_DOCS_URL));
		} break;
	}
	if (p_option != SEARCH_FIND && p_option != SEARCH_REPLACE && p_option != SEARCH_GOTO_LINE) {
		shader_editor->get_text_editor()->call_deferred(SNAME("grab_focus"));
	}
}
void TextShaderEditor::_notification(int p_what) {
	switch (p_what) {
		case NOTIFICATION_ENTER_TREE:
		case NOTIFICATION_THEME_CHANGED: {
			PopupMenu *popup = help_menu->get_popup();
			popup->set_item_icon(popup->get_item_index(HELP_DOCS), get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")));
		} break;
		case NOTIFICATION_APPLICATION_FOCUS_IN: {
			_check_for_external_edit();
		} break;
	}
}
void TextShaderEditor::_editor_settings_changed() {