Package media content metadata.
An enum with 4 variants:
| discriminant | variant | description |
|---|
| 0 | Audio | Collection of audio items. |
| 1 | Image | Collection of image items. |
| 2 | Video | Collection of video items. |
| 3 | Web | A web site, with static/index.html as its entry point. |
| n | field | type | optional | description |
|---|
| 1 | items | an array of Item<Audio> | false | Metadata describing the audio items. |
| n | field | type | optional | description |
|---|
| 1 | items | an array of Item<Image> | false | Metadata describing the image items. |
| n | field | type | optional | description |
|---|
| 1 | items | an array of Item<Video> | false | Metadata describing the video items. |