Add OCaml 5.2 and 5.3 to CI

Author: sim642

.github/workflows/ci.yml

@@ -15,6 +15,8 @@ jobs:
           - ubuntu-latest
           # - macos-latest
         ocaml-compiler:
+          - 5.3.x
+          - 5.2.x
           - 5.1.x
           - 5.0.x
           - 4.14.x