v0.9.4: Support Electron v13-14 and Node v16 (#358)

* Support Electron 13 and 14

* Support Node 16

* Drop support for unsupported target versions

https://nodejs.org/en/about/releases/
Currently supported versions of Node.js: v12 through v16

https://www.electronjs.org/docs/tutorial/support
Currently supported versions of Electron: v12, v13, and v14

* Update nan

* Fix EOL