Add an indicator to "example tracks" list when there's an overriding version in local storage

[lehnerpat]

When a user edits one of the included "example tracks", the edited version gets saved to LocalStorage, and appears (as a duplicate) in the area "Tracks saved in browser" on the start page.
At this point, opening that track always shows the version from LocalStorage, even when clicking the original entry (under "example tracks"). (The original version can only be accessed again by deleting the LocalStorage version of the track.)

To make this clearer, let's add an info marker to example tracks that have an overriding version in LocalStorage.
This marker could be a little tag saying "local" with a tooltip explaining that clicking it will open the version from LocalStorage.