clang-format: [JS] ASI insertion after boolean literals.

Summary:
Before when a semicolon was missing after a boolean literal:
    a = true
    return 1;

clang-format would parse this as one line and format as:
    a = true return 1;

It turns out that C++ does not consider `true` and `false` to be literals, we
have to check for that explicitly.

Reviewers: djasper

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D24574

llvm-svn: 281856