Make optional reporting of "import/export: Multiple exports of name ..."

[ftaiolivista]

Multiple exports of name is always reported as an error but it's a legitimate feature disciplined by ECMASCRIPT specs.

Es:

// D.js 
const f = () => 'D::f'
export { f }

// E.js
export * from './D.js'
const f = () => 'E::f'
export { f }

Report -> import/export: Multiple exports of name 'f'.

Maybe eslint-plugin-import could give an optionable error that can ben disabled by config?

See also here and #1704

[ljharb]

An option sounds good.