NATS token auth, single node support Latest

Contributed by @fkmeland:

• Updated dependencies, mostly to fix connection issues, tokio context issues
• Changed from rants to nats-async client
• Added NATS token auth
• Fixes issues with getting server stats when the NATS node is a single node and not clustered
• Updated Dockerfile to latest rust alpine image due to building issues with regex versions

v0.1 - fixed

Fix websocket issues (i.e. mixed content errors / no updates when running over HTTPS)
Run as 1000:1000
Use /data volume to persist settings
build a smallish (40MB uncompressed) alpine container

docker image: ghcr.io/thielj/nats-webui:v0.1.2 (or just :latest)