Fix docker compose file example in README.md

[FalkoFlessner]

In README.md is an example docker-compose.yaml file that can be improved in two points

• The "version" top level element is obsolete, see https://docs.docker.com/reference/compose-file/version-and-name/
• The "command" element contains a superflous "pebble" that prevents the following parameters from being parsed. (In the included docker-compose.yaml, the "command" element is already correct, see

  pebble/docker-compose.yml

  Line 5 in e08dd94

  command: -config test/config/pebble-config.json -strict -dnsserver 10.30.50.3:8053

  for comparison.)

[mcpherrinm]

Perhaps we should just remove the example from the README and reference the docker-compose.yml, as it's more likely to be tested and correct.

[FalkoFlessner]

Sounds reasonable. Do you want this to be part of this PR?

[mcpherrinm]

Let's merge this as-is, and we can always do that as another change if we want.