Add gz-jetty-* aliases

[scpeters]

Part of gazebo-tooling/release-tools#1403.

Implemented with:

pushd $(brew --repo osrf/simulation)/Aliases
COLLECTION=jetty
for f in $(grep 'depends_on.*"[gs][zd]' ../Formula/gz-${COLLECTION}.rb | sed -e 's@.* "@@' -e 's@"$@@');
do
  PKG=$(echo $f | sed -e 's@gz-@@' -e 's@[0-9]*@@g');
  echo $f $PKG;
  ln -s ../Formula/$f.rb gz-${COLLECTION}-$PKG;
done
popd