Test Rails 6.1 on CI

Author: Bart de Water

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         ruby: [2.6, 2.7, 3.0]
-        gemfile: [rails_5_2, rails_6_0, rails_edge]
+        gemfile: [rails_5_2, rails_6_0, rails_6_1, rails_edge]
         exclude:
           - ruby: 2.6
             gemfile: rails_edge