Upgrade node version to 16

[mgtitimoli]

Hello!

First of all, I would like to thank you all for the work you put on creating this amazing action!

I was wondering if is there something that prevents us to upgrade the node version to the latest LTS.

Github is deprecating Node 12 actions and moving to 16 as it says in this blog post.

If not (which I believe it's the case), I can submit a PR or directly take it anyone that would like to do so.

Thanks again!