Merge pull request #4800 from dokku/help2man-devcontainer

Add help2man os package for copyfiles make target to devcontainer

.devcontainer/Dockerfile

@@ -2,7 +2,7 @@ FROM dokku/dokku:latest
 
 RUN apt-get update
 RUN apt-get install --no-install-recommends -y build-essential file nano && \
-  apt-get install --no-install-recommends -y shellcheck uuid-runtime xmlstarlet && \
+  apt-get install --no-install-recommends -y help2man shellcheck uuid-runtime xmlstarlet && \
   apt-get clean autoclean && \
   apt-get autoremove --yes && \
   rm -rf /var/lib/apt/lists/*