codimd: build with nodejs-12_x instead of nodejs-10_x

The codimd test is now exposed via passthru.tests

pkgs/servers/web-apps/codimd/default.nix

@@ -1,5 +1,5 @@
 { stdenv, fetchFromGitHub, fetchpatch, makeWrapper
-, which, nodejs, mkYarnPackage, python2 }:
+, which, nodejs, mkYarnPackage, python2, nixosTests }:
 
 mkYarnPackage rec {
   name = "codimd";
@@ -63,6 +63,8 @@ mkYarnPackage rec {
     runHook postDist
   '';
 
+  passthru.tests = { inherit (nixosTests) codimd; };
+
   meta = with stdenv.lib; {
     description = "Realtime collaborative markdown notes on all platforms";
     license = licenses.agpl3;