Manipulation with sets

[blond]

Add static methods to created instance of HashSet:

• merge
• intersect
• subtract

const hashSet = require('hash-set');

// Create Set class which compares objects with JSON.stringify
const JSONSet = hashSet(JSON.stringify);
const set1 = new JSONSet([{ a: 1 }, { b: 2 }]);
const set2 = new JSONSet([{ c: 3 }, { b: 2 }]);

JSONSet.merge(set1, set2); // [{ a: 1 }, { c: 3 }, { b: 2 }]
JSONSet.intersect(set1, set2); // [{ b: 2 }]
JSONSet.subtract(set1, set2); // [{ a: 1 }]