[Request For Comments] fix: @flow flag does not need to be first comment

[scott-silver]

eslint-plugin-flowtype rules require that the // @flow comment be the first line of a file.

This is stricter than Flow requires (emphasis in original), which simply requires the comment appear before any code:

The Flow background process monitors all Flow files. However, how does it know which files are Flow files and, thus, should be checked? Placing the following before any code in a JavaScript file is the flag the process uses to answer that question.

1 // @flow

This PR updates noTypesMissingFileAnnotation to allows a comment to appear before the @flow comment.

This likely has more implications for requireValidFileAnnotation, however.

[scott-silver]

ping @gajus

[julienw]

thx ! Now I just need a new release :D

[gajus]

The release is done automatically after the commit is merged.

[julienw]

oh I see, thanks ! I didn't see any change to package.json, that's why I was confused.