Add hook_help() as per module documentation guidelines

Problem/Motivation

The views_block_filter_block.module does not implement hook_help(). See https://www.drupal.org/docs/develop/managing-a-drupalorg-theme-module-or...

Proposed resolution

Add hook_help() as per module documentation guidelines - https://www.drupal.org/docs/develop/managing-a-drupalorg-theme-module-or...