C++ in VSCode

Follow the official instruction
- Note that compilation is per project setting
- To use c++17, add "--std=c++17" to tasks.json
- As of 2020-12-06, there is a bug for running debugger. Have to change the label of a comilation task. But there was another issue. Thus I just ran with terminal instead.
Per Language setting:
- json
```
"[cpp]": {
    "breadcrumbs.showArrays": true,
    "editor.wordBasedSuggestions": false,
    "editor.suggest.insertMode": "replace",
    "editor.semanticHighlighting.enabled": true,
    "editor.tabSize": 2
}
```
C++ formatter
- In setting, search C_Cpp.clang_format_fallbackStyle
- Change the value to { BasedOnStyle: Google, IndentWidth: 2 } (The default one may be Visual Studio)