Add ruby 4.0 and head

Author: biow0lf

.github/workflows/rspec.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["3.1", "3.2", "3.3", "3.4"]
+        ruby: ["3.1", "3.2", "3.3", "3.4", "4.0", "head"]
 
     steps:
       - name: Harden the runner (Audit all outbound calls)