Add in some documentation on classloader and psr4
Created by: seamuslee001
@totten can you check and make sure this looks correct? @seanmadsen i think this is what is meant it relates to https://github.com/civicrm/civicrm-core/blob/ad16dd2c5345f34330cd6731dd01f7d74218d7b8/CRM/Extension/ClassLoader.php#L117 and https://github.com/civicrm/civicrm-core/blob/648631cd94799e87fe2347487d465b1a7256aa57/CRM/Extension/Info.php#L137