function stringify(theme) {
    return JSON.stringify(toJson(theme));
}
Stringifies a [[Theme]] with formatter functions to a JSON string.

```ts
import chalk = require('chalk');
import {stringify} from 'cli-highlight';
import * as fs from 'fs';

const myTheme: Theme = {
    keyword: chalk.red.bold,
    addition: chalk.green,
    deletion: chalk.red.strikethrough,
    number: plain
}
const json = stringify(myTheme);
fs.writeFile('mytheme.json', json, (err: any) => {
    if (err) throw err;
    console.log('Theme saved');
});
```