typescript: Support binding pattern in signature

[andy-ms]

Input Code

export type T = ({x, y}: any) => void;

(from babel/babel#6065 (comment))

Babylon/Babel Configuration

{
  "presets": ["typescript"]
}

Expected Behavior

Parse succeeds

Current Behavior

{ SyntaxError: src\a.ts: Unexpected token, expected ) (1:23)

Your Environment

software	version
Babylon	7.0.0-beta.29
node	8.7.0
npm	5.5.1
Operating System	Windows 10 Enterprise

(would assign myself if I could)

[hzoo]

Hey @andy-ms! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community that typically always has someone willing to help. You can sign-up here
for an invite.

[babel-bot]

This issue has been moved to babel/babel#6667.