Fix package.json engine semver ranges (node.js >=8.9 <13, yarn >=1 <2)

[jbielick]

8.16 is somewhat arbitrary as far as I can tell, so this allows earlier 8.x releases of node.js as the engine so that 8.9, 8.10, 8.12, etc from Ubuntu 18.04 LTS can install this package.

See #2228 comments for interest.

[jakeNiemiec]

Some more justification for 8.9

https://github.com/webpack-contrib/terser-webpack-plugin/releases/tag/v2.0.0
https://github.com/webpack/webpack/blob/1af81690ffc79ccf051f74d15bcefddb7ad3b2c9/package.json#L84
https://github.com/webpack-contrib/compression-webpack-plugin/blob/master/package.json#L16

Thanks for the PR, can you expand your scope to also fix the yarn engine range? I have adjusted the ranges according to https://semver.npmjs.com/ (test here) & https://nodejs.org/en/about/releases/

[jbielick]

@jakeNiemiec Great idea—updated. Thanks for the additional references and suggestions.

[jakeNiemiec]

Great, this will also fix help prevent things like:

• Add post-install messages, redo README.md and move documentation to separate file #2452 (comment)
• Webpacker issues with Rails 6.0.2.1 rails#38414 (comment)
• yarn check deprecated #2354 (comment)
• Simply depending on @rails/webpacker isn't enough? Possibly need to add all dependencies to package.json #1537 (comment)
• Yarn 2.0 (Yarn Plug’n’Play) #2112 (comment)
• Why isn't .yarn/ in .gitignore? #2446 (comment)

[jakeNiemiec]

Unless the user has set the engine-strict config flag, this field is advisory only and will only produce warnings when your package is installed as a dependency.

Something to keep in mind, but this sounds exactly like what we need.