Add Function Support

[nrdobie]

This would add support for Functions as values.

Proposed usage:

import SJSON, { registerFunction } from '@onedeadpixel/superjson'

// In application setup
registerFunction(SJSON)

const data = {
  myFunc: (status) => console.log('MY LOG:', status)
}

const jsonString = SJSON.stringify(data) // => {
//   "myFunc": {
//     "__sj_type": "Function",
//     "__sj_value": "(status) => console.log('MY LOG:', status)"
//    }
//  }

// JSON string sent to another memory instance

const data = SJSON.parse(jsonString) // => {
//   myFunc: (status) => console.log('MY LOG:', status)
// }

Possible Issues:

• Functions could pose some level of security risk so they would not be enabled by default.