fix: parse JS as Prettier's parsers do

Prettier's Babel allows return outside a function, and its TypeScript
parser reads a .d.ts, .d.mts, .d.cts or .d.x.ts file as declarations,
where a const needs no initializer. oxc now does both, so tidy formats
the corpus files it rejected. The oracle goes from 9,117 to 9,126 files
printed as Prettier prints them, and no file is worse.