Fix Error TS2306 ("flowjs/index.d.ts not a module")

[davehensley]

I was trying to import the flowjs types, but I'm unable to do so because they are not exported. So this is just a small fix to export the types.

• Use a meaningful title for the pull request. Include the name of the package modified.
• Test the change in your own code. (Compile and run.)
• Follow the advice from the readme.
• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).

Select one of these and delete the others:

If changing an existing definition:

• Provide a URL to documentation or source code which provides context for the suggested changes: https://stackoverflow.com/questions/40379116/using-flow-js-in-angular-2-typescript

[dt-bot]

types/flowjs/index.d.ts

to author (@ryan10132). Could you review this PR?
👍 or 👎?

Checklist

• pass the Travis CI test?