message: docs: fix example of Dockerfile.contrib
  First fix: If you cd into "docker", the Dockerfile is present in the same directory.
  Second fix: The branch `feat#startStop` doesn't exist, and most people must want to build master branches.
diff: @@ -190,7 +190,7 @@ The docker images are the latest stable images of the [zwavejs2mqtt](https://git
  ```bash
  git clone https://github.com/zwave-js/zwavejs2mqtt.git
  -cd zwavejs2mqtt/docker
  +cd zwavejs2mqtt
  docker build -f docker/Dockerfile --build-arg Z2M_GIT_SHA1=master -t zwavejs/zwavejs2mqtt:latest .
  ```
  @@ -231,7 +231,7 @@ git clone https://github.com/zwave-js/zwavejs2mqtt
  The run the build from outside the two repo folders.
  ```bash
  -DOCKER_BUILDKIT=1 docker build --build-arg SRC=git-clone-src --build-arg Z2M_BRANCH=feat#startStop --build-arg ZWJ_BRANCH=master --no-cache -f zwavejs2mqtt/docker/Dockerfile.contrib -t zwavejs2mqtt .
  +DOCKER_BUILDKIT=1 docker build --build-arg SRC=git-clone-src --build-arg Z2M_BRANCH=master --build-arg ZWJ_BRANCH=master --no-cache -f zwavejs2mqtt/docker/Dockerfile.contrib -t zwavejs2mqtt .
  ```
  or
  