Add VOLUME declaration for metacpan-cpan-extracted

Author: ssoriche

Dockerfile

@@ -5,4 +5,5 @@ WORKDIR /metacpan-grep-front-end
 
 RUN cpm install --without-test -g
 EXPOSE 3000
+VOLUME [ "/metacpan-cpan-extracted" ]
 CMD plackup -p 3000 ${GREP_PLACKUP_SERVER_ARGS} bin/app.psgi