v0.21.4

The request statistics that you may remember from logs are now persisted in key-value store,
so you won't lose count when your actor restarts. We've also added a lot of useful
stats in there which can be useful to you after a run finishes. Besides that,
we fixed some bugs and annoyances and improved the TypeScript experience a bit.

• Add persistence to Statistics class and automatically persist it in BasicCrawler.
• Fix issue where inaccessible Apify Proxy would cause ProxyConfiguration to throw
  a timeout error.
• Update default user agent to Chrome 85
• Bump Puppeteer to 5.2.1 which uses Chromium 85
• TypeScript: Fix RequestAsBrowserOptions missing some values and add RequestQueueInfo
  as a return value from requestQueue.getInfo()