h2o: add passthru tests

pkgs/by-name/h2/h2o/package.nix

@@ -16,6 +16,7 @@
   withMruby ? true,
   bison,
   ruby,
+  nixosTests,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -71,6 +72,10 @@ stdenv.mkDerivation (finalAttrs: {
     done
   '';
 
+  passthru = {
+    tests = { inherit (nixosTests) h2o; };
+  };
+
   meta = with lib; {
     description = "Optimized HTTP/1.x, HTTP/2, HTTP/3 server";
     homepage = "https://h2o.examp1e.net";