Release async-nats beta v0.13.0

Overview

This time around it's just async-nats Client release.

Its most important part is headers support which enables work around JetStream that first PRs should show up in next release.

Added

• Add Auth - username/password & token by @Jarema in #408
• Support sending and receiving messages with headers by @caspervonb in #402
• Add async server errors callbacks by @Jarema in #397
• Discover additional servers via INFO by @caspervonb in #403
• Resolve socket addresses during connect by @caspervonb in #403

Changed

• Wait between reconnection attempts by @caspervonb in #407
• Limit connection attempts by @caspervonb in #400

Other

• Remove redundant doctests by @Jarema in #412
• Fix connection callback tests by @Jarema in #420

Full Changelog: async-nats/v0.12.0...async-nats/v0.13.0