Add a filter hiding unmaintained apps in app list

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## Feature request

**Which Nextcloud Version are you currently using:** (see administration page)
31.0.3

**Is your feature request related to a problem? Please describe.**
Over the time so many people developed different apps for Nextcloud which is in general a good idea but as people move on to different projects there are apps which are totally outdated and unable to run on an up-to-date/maintained Nextcloud version - e.g. [Ebook reader](https://apps.nextcloud.com/apps/files_ebookreader): According to the store the last update was released 6 years ago and is compatible with Nextcloud 16.

**Describe the solution you'd like**
Remove apps which are either abandoned since several years or are no longer compatible with the last official maintained version of Nextcloud

**Describe alternatives you've considered**
Create some kind of graveyard appstore where all those non-maintained apps may be listed.