DigitalPlatformEnumeration

Enumerates some common technology platforms, for use with properties such as [[actionPlatform]]. It is not supposed to be comprehensive - when a suitable code is not enumerated here, textual or URL values can be used instead. These codes are at a fairly high level and do not deal with versioning and other nuance. Additional codes can be suggested [in github](https://github.com/schemaorg/schemaorg/issues/3057).