Test more Composer versions

Author: ondrejmirtes

.github/workflows/integration-tests.yml

@@ -27,6 +27,7 @@ jobs:
           - "v2"
           - "preview"
           - "snapshot"
+          - "2.1.0"
 
     steps:
       - name: "Checkout"
@@ -70,6 +71,7 @@ jobs:
           - "v2"
           - "preview"
           - "snapshot"
+          - "2.1.0"
 
     steps:
       - name: "Checkout"