`skipNulls` option for queryString.stringify

Hi!

I am now comparing 2 libs for future use on my project: qs and query-string. The second one has some advantages like encoding/decoding booleans and numbers which are important for me. But the 1st one has skipNulls option which allows to skip null and undefined values:

const obj1 = {
  a: 1,
  b: '2',
  c: [3, 4, 5],
  d: true,
  e: 'just string',
  f: null,
  g: undefined,
};

// qs
// can skip null/undefined values
const ex2 = qs.stringify(obj1, {
  addQueryPrefix: true,
  arrayFormat: 'comma',
  skipNulls: true,
});
const ex3 = qs.parse(ex2, {
  parseArrays: true,
  comma: true,
  ignoreQueryPrefix: true,
});

// query-string
// can store numbers and booleans
const ex4 = queryString.stringify(obj1, {
  strict: true,
});
const ex5 = queryString.parse(ex4, {
  parseNumbers: true,
  parseBooleans: true,
});

console.log('ex2', ex2);
console.log('ex3', ex3);
console.log('ex4', ex4);
console.log('ex5', ex5);

Does it sound reasonable to implement this option?

[Ashtonian]

3 separate configurable options would be very nice inspired by https://www.npmjs.com/package/qs.

{
"skipNulls" : true|false, 
"skipUndefined": true|false, // currently default
"skipEmptyStrings":true|false
}

[sindresorhus]

I think the option should be skipNullAndUndefined to make it clear what it does.