Gravatar url in typescript

gravatar-url.ts

// npm install md5
import * as md5 from 'md5';

export const enum GravatarType {
  MysteryPerson,
  Identicon,
  MonsterId,
  Wavatar,
  Retro,
  Robohash,
  Blank
}
export const enum GravatarRating {
  G,
  PG,
  R,
  X
}

const knownGravatarRatings = {
  [GravatarRating.G]: 'g',
  [GravatarRating.PG]: 'pg',
  [GravatarRating.R]: 'r',
  [GravatarRating.X]: 'x',
};

const knownGravatarTypes = {
  [GravatarType.MysteryPerson]: 'mp',
  [GravatarType.Identicon]: 'identicon',
  [GravatarType.MonsterId]: 'monsterid',
  [GravatarType.Wavatar]: 'wavatar',
  [GravatarType.Retro]: 'retro',
  [GravatarType.Robohash]: 'robohash',
  [GravatarType.Blank]: 'blank',
};

export const gravatarUrl = (email: string, size = 64, rating = GravatarRating.PG, type = GravatarType.Identicon): string => {
  const hash = md5(email);
  return `https://www.gravatar.com/avatar/${hash}?s=${size}&r=${knownGravatarRatings[rating]}&d=${knownGravatarTypes[type]}`;
};