X509 support, React support and other improvements.

What's Changed

• Use a disconnect with a non-zero reason code now that IoT Core supports it by @bretambrose in #400
• NPM update by @graebm in #411
• More usefull errors when missing data by @TwistedTwigleg in #414
• MQTT5 userguide adjustment by @TwistedTwigleg in #412
• Refactor flaky MQTT311 tests by @bretambrose in #419
• Event Stream Bindings and Tests by @bretambrose in #410
• Fix y18n version in package-lock.json by @xiazhvera in #427
• React support by @bretambrose in #428
• Remove Buffer constructor invocation by @bretambrose in #433
• Improve browser MQTT interaction with credentials refresh by @bretambrose in #431
• X509 binding by @TwistedTwigleg in #432
• Setup CI to validate lock file version by @xiazhvera in #435

Full Changelog: v1.15.9...v1.15.10