* wayland: text input protocol uses UTF-8 encoding

The Wayland text input protocol sends text in
UTF-8 encoding, but the Flutter TextInputModel
expects UTF-16.

This adds the missing conversion from UTF-8 to
UTF-16.

Signed-off-by: Sebastian Urban <surban@surban.net>

* Add Sebastian Urban to AUTHORS

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Signed-off-by: Sebastian Urban <surban@surban.net>