npm install fails due to node-gyp rebuild step depending on packages built for old versions of Node

Hi there! I'm extremely interested in using this package (it's the lightest-weight and best looking package out there) but can't install it on a current-ish version of node (e.g. node v15).

npm install openbabel fails due to node-gyp rebuild failing, due to what looks like an outdated version of the nan package built for older versions of node? Not 100% sure as I don't work with C++ builds/compiling to a node package. But I'm guessing you'll have greater insight.

> openbabel@1.2.3 install /Users/xxx/xxx-app/node_modules/openbabel
> node-gyp rebuild

  CXX(target) Release/obj.target/openbabel/src/atom.o
In file included from ../src/atom.cpp:2:
In file included from ../src/mol.h:11:
In file included from ../node_modules/nan/nan.h:111:
../node_modules/nan/nan_new.h:24:43: error: no member named 'Handle' in namespace 'v8'
template <typename T> v8::Local<T> To(v8::Handle<v8::Integer> i);
                                      ~~~~^
../node_modules/nan/nan_new.h:24:61: error: expected '(' for function-style cast or type construction
template <typename T> v8::Local<T> To(v8::Handle<v8::Integer> i);
                                                 ~~~~~~~~~~~^
../node_modules/nan/nan_new.h:24:63: error: use of undeclared identifier 'i'
template <typename T> v8::Local<T> To(v8::Handle<v8::Integer> i);

. . .
. . .
etc.
etc.

fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
make: *** [Release/obj.target/openbabel/src/atom.o] Error 1
gyp ERR! build error 
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack     at ChildProcess.onExit (/Users/xxx/.nvm/versions/node/v15.9.0/lib/node_modules/npm/node_modules/node-gyp/lib/build.js:194:23)
gyp ERR! stack     at ChildProcess.emit (node:events:378:20)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (node:internal/child_process:290:12)
gyp ERR! System Darwin 20.6.0
gyp ERR! command "/Users/xxx/.nvm/versions/node/v15.9.0/bin/node" "/Users/adam/.nvm/versions/node/v15.9.0/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /Users/xxx/xxx-app/node_modules/openbabel
gyp ERR! node -v v15.9.0
gyp ERR! node-gyp -v v5.1.0
gyp ERR! not ok 

Reproduce the npm install openbabel failure with Node v15 and inspect the native build path beginning at src/atom.cpp and src/mol.h, along with the reported node_modules/nan/nan.h errors. Done means the package installs and node-gyp rebuild completes successfully on a current Node version.