### 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)

disabled_branch_regions.clear();
	clear_highlighting_cache();
}
void GDShaderSyntaxHighlighter::set_disabled_branch_color(const Color &p_color) {
	disabled_branch_color = p_color;
	clear_highlighting_cache();
}
static bool saved_warnings_enabled = false;
static bool saved_treat_warning_as_errors = false;
static HashMap<ShaderWarning::Code, bool> saved_warnings;
static uint32_t saved_warning_flags = 0U;
void ShaderTextEditor::_notification(int p_what) {
	switch (p_what) {
		case NOTIFICATION_THEME_CHANGED: {
			if (is_visible_in_tree()) {
				_load_theme_settings();
				if (warnings.size() > 0 && last_compile_result == OK) {
					warnings_panel->clear();
					_update_warning_panel();
				}
			}
		} break;
	}
}
Ref<Shader> ShaderTextEditor::get_edited_shader() const {