Write UTF-8 data to the clipboard.

[snianu]

Popular native apps on Windows read formats like image/svg+xml in UTF-8 form [1]. In the spec, before the payload for a format gets written to the clipboard, the content is converted from UTF-8 into scalar values. Spec text "Let payload be the result of UTF-8 decoding item’s underlying byte sequence."(https://w3c.github.io/clipboard-apis/#write-blobs-and-option-to-the-clipboard). Should this text be changed to write UTF-8 encoded data directly to the clipboard?

[1] https://docs.google.com/document/d/1ULlihA0FOJOqcyD9MgzLZrAbk0uTQPJqDPuPJ2aiuS4/edit?usp=sharing