Add all OCaml 5 versions to CI

Author: tmcgilchrist

.github/workflows/main.yml

@@ -15,9 +15,11 @@ jobs:
     strategy:
       matrix:
         ocaml-compiler:
+          - 5.0
           - 5.1
           - 5.2
           - 5.3
+          - 5.4
         os:
           - ubuntu-latest
           - macos-15