steamrt-dev: Add fish, an interactive shell
Requested by @timothee.besset-ext on https://phabricator.collabora.com/T14485
This MR is not enough: it will also be necessary to add a bunch of dependencies at their unmodified Ubuntu 18.04 versions to spy (I tried adding bc, lynx, man-db, jquery and pcre2 to my branch; found out that those pull in bsdmainutils, groff-base and libpipeline; then gave up because the cost/benefit ratio wasn't looking great).
Edited by Lucas Kanashiro