### 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)

if (shader.is_valid()) {
		_reload_shader_from_disk();
	} else if (shader_inc.is_valid()) {
		_reload_shader_include_from_disk();
	}
}
void TextShaderEditor::edit(const Ref<Shader> &p_shader) {
	if (p_shader.is_null() || !p_shader->is_text_shader()) {
		return;
	}
	if (shader == p_shader) {
		return;
	}
	shader = p_shader;
	shader_inc = Ref<ShaderInclude>();
	shader_editor->set_edited_shader(shader);
}
void TextShaderEditor::edit(const Ref<ShaderInclude> &p_shader_inc) {
	if (p_shader_inc.is_null()) {
		return;
	}
	if (shader_inc == p_shader_inc) {
		return;
	}
	shader_inc = p_shader_inc;
	shader = Ref<Shader>();
	shader_editor->set_edited_shader_include(p_shader_inc);
}
void TextShaderEditor::save_external_data(const String &p_str) {