Node.js v16

[caoccao]

I tried latest Node.js v16 on Linux yesterday. Here are my thoughts for your reference.

1. There were a few warnings because some Node.js v14 API are deprecated in v16. Luckily, the build passed.
2. The Javet unit test all passed. So, there's no technical issue in upgrading to v16.
3. I don't plan to upgrade to v16 before v16 becomes LTS. Backward compatibility is my major concern on that.

[caoccao]

Node.js 16 is now supported.