fix(build/docker): Bump node from 10.x to 12.x

[carlosdagos]

Following the documented way to build from source using docker fails because the version of Node used is deprecated.

Bumping to the currently supported version 12.x solves the problem and allows building from source.

P.S.: Thank you for this project! :)

[carlosdagos]

This might require some additional update to docs maybe?

[chana1024]

hey guy!i get the error it is the same with your problem?

[despairblue]

I build from master today, and I had no issues with the node.js version.

@carlosdagos What's the error you're getting?

[despairblue]

@chana1024 you're error looks like it's complaining about having not internet access.

[carlosdagos]

Hey @chana1024, no that definitely was not the error I got 😄

@despairblue, I don't quite recall now which error exactly I got, but the current Node 10.x script contains the following deprecation warning

"                         SCRIPT DEPRECATION WARNING                         " "\
This script, located at ${bold}https://rpm.nodesource.com/setup${normal}, used to
  install Node.js v0.10, is deprecated and will eventually be made inactive.

  You should use the script that corresponds to the version of Node.js you
  wish to install. e.g.

   * ${green}https://rpm.nodesource.com/setup_12.x - Node.js v12 LTS \"Erbium\"${normal}
   * ${green}https://rpm.nodesource.com/setup_14.x - Node.js v14 LTS \"Fermium\"${normal} (recommended)
   * ${green}https://rpm.nodesource.com/setup_16.x - Node.js v16 \"Gallium\"${normal}

  Please see ${bold}https://github.com/nodejs/Release${normal} for details about which
  version may be appropriate for you.

  The ${bold}NodeSource${normal} Node.js Linux distributions GitHub repository contains
  information about which versions of Node.js and which Linux distributions
  are supported and how to use the install scripts.
    ${bold}https://github.com/nodesource/distributions${normal}
"

Thanks!