Fix word duplication at wrap boundaries

suggestLineBreak returns an absolute position, but it was passed
directly as a length to NSRange. On the first fragment this works by
coincidence (position equals length when starting at 0), but on
subsequent fragments the length is too large by startOffset, causing
each CTLine to include characters already rendered in the previous
fragment.

Cherry-pick of CodeEditApp#122
Fixes CodeEditApp/CodeEditSourceEditor#367

Author: kunaldeo

Sources/CodeEditTextView/TextLine/Typesetter/Typesetter.swift

@@ -181,7 +181,9 @@ final public class Typesetter {
             )
 
             // Indicates the subrange on the range that the typesetter knows about. This may not be the entire line
-            let typesetSubrange = NSRange(location: context.currentPosition - range.location, length: lineBreak)
+            // Convert the absolute position to an offset relative to the typesetter's range.
+            let startOffset = context.currentPosition - range.location
+            let typesetSubrange = NSRange(location: startOffset, length: lineBreak - startOffset)
             let typesetData = typesetLine(typesetter: typesetter, range: typesetSubrange)
 
             // The typesetter won't tell us if 0 characters can fit in the constrained space. This checks to