These annotations make it clear to the reader of a JavaScript source
where the build process outputs to. These annotations can later be
integrated in a webpack configuration. This way there is one source of
truth.
The `build` folder is omitted from the paths, because a single JS file
shouldn't not be responsible of knowing where outputs in general will
end up at. A file only knows its output location relative to the
project.
Props adamsilverstein, herregroen, omarreiss, pento.
Fixes#44361.
git-svn-id: https://develop.svn.wordpress.org/trunk@43347 602fd350-edb4-49c9-b593-d223f7449a82
78f2b0e731