MQTT5 fixes

What's Changed

• Add proxy support to Greengrass Discovery by @TwistedTwigleg in #377
• New CD workflow by @TwistedTwigleg in #371
• MQTT5 Userguide Update by @sbSteveK in #379
• Custom auth websocket support by @TwistedTwigleg in #367
• Update submodules to latest release by @TwistedTwigleg in #386
• Fix minor mistake in release YAML by @TwistedTwigleg in #387
• AutoTag PR for v1.12.1 by @TwistedTwigleg in #388

Full Changelog: v1.12.0...v1.12.1