clang-format: [JS] do not wrap ES6 imports/exports.

"import ... from '...';" and "export ... from '...';" should be treated
the same as goog.require/provide/module/forwardDeclare calls.

Patch by Martin Probst.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@264055 91177308-0d34-0410-b5e6-96231b3b80d8