v0.8.21: Merge pull request #1876 from uProxy/fix-typings-cca

Update to uproxy-lib v31.0.0. Release notes from uproxy-lib:

• We've introduced active queue management (AQM) between two key parts of our system: churn, our network traffic obfuscation workhorse, and freedomjs, our message passing nerve centre. AQM selectively drops network packets when the system is under load, acting as a safety release valve for the proxy as a whole. While this currently incurs a 5-10% throughput penalty, there's a noticeable effect on reliability, particularly for Firefox users fetching complex pages.
• A new helper class, SignalBatcher, batches and compresses (with the gzip algorithm) signalling channel messages. Currently in use only by the copy/paste sample app, this will help us cut the size of our one-time connection messages approximately in half.
• PeerConnection now caps the maximum number of channels to that specified by the browser during connection negotiation -- additionally, the SOCKS proxy now sends an error to the browser once that cap is reached. Together, these changes help prevent the "infinite loading time" we've seen on very complex pages, especially on Firefox which has a low channel number limit.
• Our network traffic obfuscation infrastructure, churn, now caps the time spent gathering ICE candidates to three seconds. This will help prevent connection establishment failures in the presence of slow STUN servers.
• TypeScript definitions for freedomjs modules are now part of and fetched from DefinitelyTyped.