### 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)

_load_theme_settings();
	get_text_editor()->set_text(p_code);
	get_text_editor()->clear_undo_history();
	get_text_editor()->call_deferred(SNAME("set_h_scroll"), 0);
	get_text_editor()->call_deferred(SNAME("set_v_scroll"), 0);
	get_text_editor()->tag_saved_version();
	_validate_script();
	_line_col_changed();
}
void ShaderTextEditor::reload_text() {
	ERR_FAIL_COND(shader.is_null());
	CodeEdit *te = get_text_editor();
	int column = te->get_caret_column();
	int row = te->get_caret_line();
	int h = te->get_h_scroll();
	int v = te->get_v_scroll();
	te->set_text(shader->get_code());
	te->set_caret_line(row);
	te->set_caret_column(column);
	te->set_h_scroll(h);
	te->set_v_scroll(v);
	te->tag_saved_version();
	update_line_and_column();
}
void ShaderTextEditor::set_warnings_panel(RichTextLabel *p_warnings_panel) {
	warnings_panel = p_warnings_panel;
}
void ShaderTextEditor::_load_theme_settings() {