undpaul: Information for Drupal 9 upgrades from Drupal 8

Drupal is facing an end-of-life this year: Support for Drupal 8 will be discontinued as of 11/2/2021. Since Drupal 8 will no longer be supported after the EOL, we can only urge all Drupal 8 site owners to upgrade their system to Drupal 9 in time.