Merge pull request #3212 from travis-ci/ga-jammy_link

added jammy link in linux reference

Author: stan-travis

user/reference/linux.md

@@ -9,6 +9,7 @@ layout: en
 This page gives an overview of the different Ubuntu Linux distributions you can use as your CI environment.
 
 You can choose one of the following distributions:
+* [Ubuntu Jammy 22.04](/user/reference/jammy/)
 * [Ubuntu Focal 20.04](/user/reference/focal/)
 * [Ubuntu Bionic 18.04](/user/reference/bionic/)
 * [Ubuntu Xenial 16.04](/user/reference/xenial/) **default**