### 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)

syntax_highlighter->add_keyword_color(E, control_flow_keyword_color);
	}
	
	
	List<String> built_ins;
	if (shader_inc.is_valid()) {
		for (int i = 0; i < RenderingServer::SHADER_MAX; i++) {
			for (const KeyValue<StringName, ShaderLanguage::FunctionInfo> &E : ShaderTypes::get_singleton()->get_functions(RenderingServer::ShaderMode(i))) {
				for (const KeyValue<StringName, ShaderLanguage::BuiltInInfo> &F : E.value.built_ins) {
					built_ins.push_back(F.key);
				}
			}
			const Vector<ShaderLanguage::ModeInfo> &modes = ShaderTypes::get_singleton()->get_modes(RenderingServer::ShaderMode(i));
			for (int j = 0; j < modes.size(); j++) {
				const ShaderLanguage::ModeInfo &mode_info = modes[j];
				if (!mode_info.options.is_empty()) {
					for (int k = 0; k < mode_info.options.size(); k++) {
						built_ins.push_back(String(mode_info.name) + "_" + String(mode_info.options[k]));
					}
				} else {
					built_ins.push_back(String(mode_info.name));
				}
			}
		}
	} else if (shader.is_valid()) {
		for (const KeyValue<StringName, ShaderLanguage::FunctionInfo> &E : ShaderTypes::get_singleton()->get_functions(RenderingServer::ShaderMode(shader->get_mode()))) {
			for (const KeyValue<StringName, ShaderLanguage::BuiltInInfo> &F : E.value.built_ins) {
				built_ins.push_back(F.key);
			}
		}