Adds a container to the docker-dev setup to run a nginx server to host the extracted
maven index file. This "external" server is required to run the maven-lister.
The served directory is in conf/maven-index, feel free to use any fld file instead.
Command used to run the lister:
swh scheduler task add list-maven-full url=https://repo1.maven.org/maven2/ index_url=http://swh-lister-maven-nginx/export.fld
Related to T1724