Ignore file systems in service worker

[cyrilletuzi]

Same as #144, but which has been closed without a fix, and it doesn't feel right.

For user specific files (like .htaccess), it's normal to have a manual config (especially when it's not supposed to happen if you use Angular CLI, as such files won't be in the dist directory).

But for common system files like .DS_Store and Thumbs.db, it should be automatic, as Angular CLI automatically add these to .gitignore. Especially when the CLI automatically copy the assets files (including the hidden file systems), so currently the service worker manifest will include them, but they may be not be deployed to the server. So a file will be missing, then the worker installation will fail and so all the offline feature won't work.

I could do the PR but I would need an indication about the file to change (not sure about this).

[cyrilletuzi]

Closing as service worker in now in main Angular repo, but the issue is still there.