chore: enable build for the 2.1 branch (#117)

Author: platosha

.github/workflows/validation.yml

@@ -2,12 +2,12 @@ name: Validation
 
 on:
   push:
-    branches: ['main', '1.3', '2.0']
+    branches: ['main', '1.3', '2.0', '2.1']
     paths-ignore:
       - 'README.md'
       - '.github/ISSUE_TEMPLATE/*'
   pull_request:
-    branches: ['main', '1.3', '2.0']
+    branches: ['main', '1.3', '2.0', '2.1']
     paths-ignore:
       - 'README.md'
       - '.github/ISSUE_TEMPLATE/*'