Writes an annotation/event to the file
edfwrite_annotation_utf8(edf_handle, onset, duration, description)
: integer containing the file handle of the opened edf/bdf-file.
: onset is relative to the starttime and startdate of the file in units of Seconds! resolution is 0.0001 second! .
: duration are in units of Seconds! resolution is 0.0001 second! If duration is unknown or not applicable: set a negative number (-1)
: UTF8-string containing the text that describes the event.
Writes an annotation/event to the file. This function is optional and can be called only after opening a file in writemode and before closing the file