Install unzip for erlef/setup-beam action

Author: sgerrand

.github/workflows/ci.yml

@@ -49,6 +49,8 @@ jobs:
     env:
       MIX_ENV: test
     steps:
+      # Needed by erlef/setup-beam action
+      - run: apt install -qqy unzip
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
         with: