iodé blocker: hide app from stream tab

Currently, it is possible to only show a single app in the "stream" tab of the iodé blocker by pressing Add filter by app. It has been suggested to also have a Hide app option. This way "spammy" apps that flood the Stream tab won't make it hard to see more useful entries from other apps.

Original suggestion: https://community.iode.tech/t/iode-app-feature-request/6115