clang-format: [JS] keep triple slash directives intact.

Summary:
TypeScript uses triple slash directives of the form:
    /// <reference path="..."/>

For various non-source instructions that should not be wrapped.

Reference:
https://www.typescriptlang.org/docs/handbook/triple-slash-directives.html

Reviewers: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D32997

llvm-svn: 302523