Use code runner on selected lines with preload of some node libraries

Hi, great job on plugin !

i looked for issue who explain if it's possible to preload require library before execute piece of code.

Actually select this in my file for test :
```
const {mocks} = require('../mock/index')
var jsonata = require("jsonata");
console.log(jsonata(`products.description`).evaluate(mocks.products));
```

It's possible to always preload

```
const {mocks} = require('../mock/index')
var jsonata = require("jsonata");
```

So in file i will can select only
```
console.log(jsonata(`products.description`).evaluate(mocks.products));
```

with code-runner.executorMap maybe ?

Thanks !