Document why each composer dependency is present

[stevector]

I think we should document why each package in require and require-dev is present. Doing so should make maintaining copies of this example easier on developers. I think the exercise will also lead us to finding that some packages are not necessary or are duplicative of others.

[ChristopherMatthews]

I agree, I started a new site this morning and manually removed the following packages as they are not really "required", but are more "recommended" or "suggested" packages.

• drupal/config_direct_save
• drupal/config_installer
• drupal/console and its dependencies