Function add_media_folder_meta

Add meta data field to a folder.

Folder meta data is called "Custom Fields" on the Administration Screen.

Returns: int|false Meta ID on success, false on failure.
Located at meta.php

Parameters summary

`integer`	`$folder_id`	Folder ID.
`string`	`$meta_key`	Metadata name.
`mixed`	`$meta_value`	Metadata value. Must be serializable if non-scalar.
`boolean`	`$unique = false`	Whether the same key should not be added.