Update default settings of code-runner.executorMap to support c++11 or higher versions

Could you please add "-std=c++11" or the higher version to code-runner.executorMap in the default settings?

It doesn't recognize many improvements in C++ after c++11, and fails. I am very new to VS Code and spent several hours to figure this out.

```
"code-runner.executorMap": {
...
"cpp": "cd $dir && g++ -std=c++11 $fileName -o $fileNameWithoutExt && $dir$fileNameWithoutExt",
...
```