Add lint rule to disallow `require.ensure`

[Timer]

We need a lint rule that will error when require.ensure is used.
Users should use import() instead.

[tharakawj]

I would like to work on this.

Apparently, there is no such a rule comes with eslint-plugin-import. So I'll send a PR to eslint-plugin-import repo first and update eslint-config-react-app accordingly. Is that the correct path to take on this issue? (I'm asking this because I'm new to open source and this project)

[ljharb]

Per import-js/eslint-plugin-import#743 (comment), eslint core already supports no-restricted-properties which can easily block both require.ensure and System.import.

[tharakawj]

@ljharb Thanks for pointing it out. I'll use no-restricted-properties rule and send a PR.