media-types.md: add foreign descriptor media type

Signed-off-by: Antonio Murdaca <[email protected]>

Author: runcom

media-types.md

@@ -3,6 +3,7 @@
 The following `mediaType` MIME types are used by the formats described here, and the resources they reference:
 
 - `application/vnd.oci.descriptor.v1+json`: [Content Descriptor](descriptor.md)
+- `application/vnd.oci.descriptor.foreign.v1+json`: [Content Descriptor](descriptor.md)
 - `application/vnd.oci.image.manifest.list.v1+json`: [Manifest list](manifest.md#manifest-list)
 - `application/vnd.oci.image.manifest.v1+json`: [Image manifest format](manifest.md#image-manifest)
 - `application/vnd.oci.image.serialization.rootfs.tar.gzip`: ["Layer", as a gzipped tar archive](serialization.md#creating-an-image-filesystem-changeset)