Merge pull request #23 from cvmfs-contrib/add-ubuntu-22.04

ci(chore): replace ubuntu-18.04 with ubuntu-22.04

Author: wdconinc

.github/workflows/ubuntu.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, ubuntu-18.04, ubuntu-20.04]
+        os: [ubuntu-latest, ubuntu-20.04, ubuntu-22.04]
     steps:
     - uses: actions/checkout@v2
     - uses: ./