Specify dashboard port for docker container

**Describe the problem you have/What new integration you would like**

I'd like the possibility to specify the dashboard port number in the docker container. We can already put our username and password in an environment variable, so why not the port number?

**Please describe your use case for this integration and alternatives you've tried:**

I always move away from standard port numbers on any docker container I use, but with the esphome docker container, this is not possible.
One workaround is to add this command to the compose file:
```
command: "dashboard /config --port ${ESPHOME_PORT} --username ${ESPHOME_USER} --password ${ESPHOME_PASS}"
```
The dashboard is started this way with my specified port number, but now the healtcheck fails as this is still done on port 6052.

**Additional context**

Start by reviewing the Docker Compose workaround in the issue: `dashboard /config --port ${ESPHOME_PORT} --username ${ESPHOME_USER} --password ${ESPHOME_PASS}`. Check how the container healthcheck still targets port 6052, and consider the environment-variable and healthcheck behavior together; done means a configured dashboard port works without a failing healthcheck.

Written by the indexing model from the issue text.