Consider adding support for re-exports to `no-types-missing-file-annotation`

[pascalduez]

Hi,

the no-types-missing-file-annotation does not support re-exports declarations, although this is quite an handy pattern. I've been caught a couple of times with this (forgetting the flow file declaration in an index), and such warning would have been of great help.

`Button.js`

// @flow

export type Props = { ... }

`index.js`

export type { Props } from './Button.js';

--> Should warn for missing flow file declaration.

[pascalduez]

eslint-plugin-flowtype@2.33.0

;)

[gajus]

Thank you, @pascalduez