Unignore the locale-data/ from npm package so its contents can be served

Currently the Bower package contains locale-data/ dir, and even though
the npm package contains `Intl.complete.js`, it's not practical to serve
because of its size. Including the locale-data/ dir makes it easier for
people to efficiently serve `Intl.min.js` along with a negotiated locale
resource pack.

Author: ericf

.npmignore

@@ -10,9 +10,6 @@ cldr/
 # d8 artifact
 .d8_history
 
-# Locale data is already present in Intl.complete.js
-locale-data/
-
 # The NPM package only needs runtime files.
 # (It doesn't need anything used during development of this library.)
 tools/