bring NodeJS framework up-to-date to work with `node:latest`

[mlp6]

We've held this back at NodeJS 8.x to avoid problems with a lot of npm packages that were not working with the latest NodeJS. Probably need to fix this now as other things need updating too. Some initial warnings to hash out at the same time:

npm WARN deprecated extract-text-webpack-plugin@1.0.1: Deprecated. Please use https://github.com/webpack-contrib/mini-css-extract-plugin
npm WARN deprecated browserslist@1.4.0: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
npm WARN deprecated formatio@1.1.1: This package is unmaintained. Use @sinonjs/formatio instead
npm WARN deprecated samsam@1.1.2: This package has been deprecated in favour of @sinonjs/samsam
npm WARN deprecated browserslist@1.7.7: Browserslist 2 could fail on reading Browserslist >3.0 config used in other tools.
npm WARN deprecated samsam@1.1.3: This package has been deprecated in favour of @sinonjs/samsam
npm WARN deprecated core-js@1.2.7: core-js@<2.6.8 is no longer maintained. Please, upgrade to core-js@3 or at least to actual version of core-js@2.
npm WARN deprecated istanbul@0.4.5: This module is no longer maintained, try this instead:
npm WARN deprecated   npm i nyc
npm WARN deprecated Visit https://istanbul.js.org/integrations for other alternatives.
npm WARN deprecated flatten@1.0.2: I wrote this module a very long time ago; you should use something else.