[DS-2052] @mire Mirage 2 Contribution

[DS-2052] @mire Mirage 2 Contribution, for more info view: https://jira.duraspace.org/browse/DS-2052
Looks like the aspect is also mentioned in the README ("Enabling the theme" section), so that's another minor thing to cleanup: https://github.com/atmire/DSpace/blob/mirage2-contribution/dspace-xmlui-mirage2/readme.md#enabling-the-theme