ENYO-578: Include renamed file in manifest.

### Issue
We had renamed `sample.css` to `Sample.css` via https://github.com/enyojs/moonstone/commit/463d1d but did not update `package.js`, resulting in some minification errors that did not stop the build process. This ultimately led to the Sampler application not appearing in the builds.

### Fix
Update `package.js` with the renamed file.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>