Add print_media_templates action to allow custom templates to be added. props ocean90. fixes #22565, see #21390.

git-svn-id: https://develop.svn.wordpress.org/trunk@22832 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/media.php

@@ -1887,4 +1887,6 @@ function wp_print_media_templates( $attachment ) {
 		</style>
 	</script>
 	<?php
+
+	do_action( 'print_media_templates' );
 }