Merge branch 'block-behavior' into 'develop'

Configurable block visibility, fixes #2123

Closes #2123

See merge request pleroma/pleroma!3242

diff --cc CHANGELOG.md
Simple merge

diff --cc config/config.exs
Simple merge

diff --cc config/description.exs
Simple merge

diff --cc docs/configuration/cheatsheet.md
Simple merge

diff --cc lib/pleroma/notification.ex
Simple merge

diff --cc lib/pleroma/web/activity_pub/activity_pub.ex
Simple merge

diff --cc test/pleroma/web/mastodon_api/controllers/notification_controller_test.exs
Simple merge

diff --cc test/pleroma/web/mastodon_api/controllers/timeline_controller_test.exs
Simple merge