codimd: js-sequence-diagrams: use git source rather than the NPM tarball

It seems as NPM just removed the tarballs of the unpublished package,
hence `codimd` isn't buildable. The sources for the package are
available on github[1] and fix the build.

For further information about the `js-sequence-diagrams` workarounds,
please refer to 5feec42.

[1] https://github.com/Moeditor/js-sequence-diagrams

pkgs/servers/web-apps/codimd/js-sequence-diagrams/default.nix

@@ -11,9 +11,11 @@ in
     name = "js-sequence-diagrams";
     packageName = "js-sequence-diagrams";
     version = "1000000.0.6";
-    src = pkgs.fetchurl {
-      url = "https://registry.npmjs.org/js-sequence-diagrams/-/js-sequence-diagrams-1000000.0.6.tgz";
-      sha1 = "e95db01420479c5ccbc12046af1da42fde649e5c";
+    src = pkgs.fetchFromGitHub {
+      owner = "Moeditor";
+      repo = "js-sequence-diagrams";
+      rev = "4d46bc6229a3f93c9bcad561cab4924034f5456d";
+      sha256 = "09ri5cx5yq87p3nla06gs0xb2gifmsy0xhs0s5524xr4ya6pnivv";
     };
     dependencies = [ ];
     dontNpmInstall = true;