Minimal version of node js for build

[SchDen]

I tried to build by npm run build:dist:chrome on node v12.22.12, it failed with error

await webExt.main(absolutePackageDir);
^^^^^

SyntaxError: Unexpected reserved word

I solved it by set node to v14.20.0.

Could we setup engine in the package.json to 14:

  "engines": {
    "node": "14"
  }

It can works with scripts for auto-switch node version (like this)[https://johnlindquist.com/automatically-switch-node-versions-based-on-your-packagejson-and-precmd-in-zsh/]