Update nodejs version

[fgaz]

Nodejs 14 is end of life.
I'd like to build with a supported node version, but I'm getting compile errors because of the four-years-old nan dependency:

npm ERR! ../../nan/nan_typedarray_contents.h: In constructor 'Nan::TypedArrayContents<T>::TypedArrayContents(v8::Local<v8::Value>)':
npm ERR! ../../nan/nan_typedarray_contents.h:34:43: error: 'class v8::ArrayBuffer' has no member named 'GetContents'
npm ERR!    34 |       data   = static_cast<char*>(buffer->GetContents().Data()) + byte_offset;
npm ERR!       |                                           ^~~~~~~~~~~

Updating node and other dependencies to current versions would be nice.

[b-g]

Sorry! This is not a low priority for us. Already hard to keep the beast going. Happy to get help a PR on this.