Add OTP 28 to CI

Author: solnic

.github/workflows/main.yml

@@ -23,11 +23,16 @@ jobs:
         include:
           # Newest supported Elixir/Erlang pair.
           - elixir: '1.18'
-            otp: '27.2'
+            otp: '28.0'
             lint: true
             dialyzer: true
             os: ubuntu-latest
 
+          - elixir: '1.18'
+            otp: '27.2'
+            lint: true
+            os: ubuntu-latest
+
           # One version before the last supported one.
           - elixir: '1.17'
             otp: '26.2'