mixin.php
Auto-register "**.mgd.php" files.
The older (mgd-php@1) and newer (mgd-php@2) are similar in that both load *.mgd.php files.
However, they differ in how the search:
- v1.x does a broad search over the entire extension source-tree.
- v2.x does a narrower search in folders which commonly have mgds.
Within 2.x, future increments may add other paths (after vetting
universefor impacts).