Add promise support to `ClipboardItem` object. This helps the web author to call async clipboard write method without having to provide the Blob data synchronously. Authors can choose to resolve the promise later when the Blob data is available.
When async clipboard.write API is called, web developers would want to provide a promise to a Blob type instead of synchronously populating the Blob data while writing it to the clipboard. This helps in performance and gives the web authors the flexibility to call write method(satisfying the requirements of calling clipboard write API) without blocking on populating the Blob data that is part of the ClipboardItem.
Explainers: https://www.w3.org/TR/clipboard-apis/#typedefdef-clipboarditemdata