Mark expired items as stale

#6 Fix ArgumentCountError for Redis::sAdd() in RedisStorage

When RedisStorage::set(Cache $item, array $tags) is called with an empty $tags array we get an ArgumentCountError error. This only happens on phpredis >= 6.0.0.

We fix this by wrapping the relevant sAdd() method in an if-block

Add wmcontroller_redis:mark-expired command to mark stale content as …

…expired

Update CHANGELOG.md

Update CHANGELOG

Bump to PHP 8.0 and Drupal 9.1

Fix incompatibility with versions under 8.7.7

Make compatible with d9

Add d9 composer compatibility

Mark as compatible with wmcontroller 0.10