feat: upgrade to node.js 16 to support ES modules by default

This will help upgrading dependencies to new versions that are exported
as ESM.

BREAKING CHANGE: Node.js version used on the action updated from 12 to
16

Author: wagoid

Dockerfile

@@ -1,4 +1,4 @@
-FROM node:12-alpine3.9
+FROM node:16-alpine3.13
 
 RUN apk --no-cache add git