message: Update Dockerfile for dotnet 3.1
  Been using this for afew weeks now, seems stable.
diff: @@ -18,7 +18,7 @@ RUN runDeps="hunspell \
  libssl1.1 \
  inotify-tools \
  patch \
  - dotnet-sdk-3.0" \
  + dotnet-sdk-3.1" \
  installDeps="ca-certificates wget gpg apt-transport-https" \
  && apt-get update \
  && apt-get install -y --no-install-recommends $installDeps \
  