Starts live spelling check (runs a live spelling thread).
(introduced in v1.9)
OnSpellingCheck event must be assigned.
If live spelling thread is already active, this method clears all live spelling underlines and restarts the thread from the beginning of document.
Note: If you use RichViewActions and want to start live spelling immediately when document is loaded, call StartLiveSpelling in TrvActionOpen.OnOpenFile.
See also property of TRichViewEdit: