some docs (also closes #974)

contrib/docker/README.md

@@ -2,10 +2,10 @@ ebusd Docker image
 ==================
 
 An [ebusd](https://github.com/john30/ebusd/) Docker image is available on the
-[Docker Hub](https://hub.docker.com/r/john30/ebusd/) and is able to download the latest released German
-[configuration files](https://github.com/john30/ebusd-configuration/) from a dedicated webservice.
+[Docker Hub](https://hub.docker.com/r/john30/ebusd/) and is able to download the latest released
+[configuration files](https://github.com/john30/ebusd-configuration/) from a [dedicated webservice](https://cfg.ebusd.eu/).
 
-It allows you to run ebusd without actually installing (or even building) it on your system.
+It allows running ebusd without actually installing (or even building) it on the host.
 You might even be able to run it on a non-Linux operating system, which is at least known to
 work well on a Synology Diskstation as well as Windows with Docker Desktop.
 
@@ -21,15 +21,14 @@ The image is able to run on any of the following architectures and the right ima
 * arm32v7
 * arm64v8
 
-Due to changes of docker hub policies, the development set of images with "devel" tag are currently not automatically
-built with every commit to the git repository. Run the following command to use it: 
+In addition to the default "latest" tag, a development set of images is available with "devel" tag. This is built
+automatically from the latest source on the git repository. Run the following command to use it: 
 
 > docker pull john30/ebusd:devel
 
 
 Running interactively
 ---------------------
-
 To run an ebusd container interactively, e.g. on serial device /dev/ttyUSB1, use the following command:
 > docker run --rm -it --device=/dev/ttyUSB1:/dev/ttyUSB0 -p 8888 john30/ebusd
 
@@ -38,7 +37,6 @@ This will show the ebusd output directly in the terminal.
 
 Running in background
 ---------------------
-
 To start an ebusd container and have it run in the background, e.g. on serial device /dev/ttyUSB1, use the following command:
 > docker run -d --name=ebusd --device=/dev/ttyUSB1:/dev/ttyUSB0 -p 8888 john30/ebusd
 
@@ -50,7 +48,6 @@ In order to get the log output from ebusd, use the following command:
 
 Using a network device
 ----------------------
-
 When using a network device, the "--device" argument to docker can be omitted, but the device information has to be
 passed on to ebusd:
 > docker run --rm -it -p 8888 john30/ebusd --scanconfig -d 192.168.178.123:10000 --latency=20
@@ -74,7 +71,7 @@ Instead of passing arguments (at the end of docker run) to ebusd, almost all (lo
 environment variables with the prefix `EBUSD_`, e.g. the following line can be used instead of the last example above:
 > docker run -d --name=ebusd --device=/dev/ttyUSB0 -p 8888 -e EBUSD_SCANCONFIG= -e EBUSD_DEVICE=/dev/ttyUSB0 -e EBUSD_MQTTPORT=1883 -e EBUSD_MQTTHOST=BROKERHOST john30/ebusd
 
-This eases use of e.g. docker-compose files.
+This eases use of e.g. "docker-compose.yaml" files like [the example docker-compose file](https://github.com/john30/ebusd/blob/master/contrib/docker/docker-compose.example.yaml) also describing each available environment variable in it.
 
 
 Running newer images on older operating systems

contrib/docker/docker-compose.example.yaml

@@ -1,5 +1,6 @@
 services:
   ebusd:
+    # alternatively, use "john30/ebusd:devel" for the latest build of the current source code
     image: john30/ebusd
     container_name: ebusd
     restart: unless-stopped