clang-format: [JS] support goog.requireType.

Summary:
It's a new primitive for importing symbols, and should be treated like
the (previously handled) `goog.require` and `goog.forwardDeclare`.

Reviewers: krasimir

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D56385

llvm-svn: 350516