4.0.0

This release is geared around overhauling the public api for this library. Many
options have been introduced over the years and this has lead to some inconsistencies
that make the library hard to use. Most have been cleaned up but a couple notable
items remain, including the confusing names of buildSitemapIndex and createSitemapIndex

• A new experimental CLI
  • stream in a list of urls stream out xml
  • validate your generated sitemap
• Sitemap video item now supports id element
• Several schema errors have been cleaned up.
• Docs have been updated and streamlined.

breaking changes

• lastmod option parses all ISO8601 date-only strings as being in UTC rather than local time
  • lastmodISO is deprecated as it is equivalent to lastmod
  • lastmodfile now includes the file's time as well
  • lastmodrealtime is no longer necessary
• The default export of sitemap lib is now just createSitemap
• Sitemap constructor now uses a object for its constructor

  const { Sitemap } = require('sitemap');
  const siteMap = new Sitemap({
    urls = [],
    hostname: 'https://example.com', // optional
    cacheTime = 0,
    xslUrl,
    xmlNs,
    level = 'warn'
  })

• Sitemap no longer accepts a single string for its url
• Drop support for node 6
• Remove callback on toXML - This had no performance benefit
• Direct modification of urls property on Sitemap has been dropped. Use add/remove/contains
• When a Sitemap item is generated with invalid options it no longer throws by default
  • instead it console warns.
  • if you'd like to pre-verify your data the validateSMIOptions function is
    now available
  • To get the previous behavior pass level createSitemap({...otheropts, level: 'throw' }) // ErrorLevel.THROW for TS users
    #215 has all the changes