Typo in exception message.

Author: Gerardwx

richtextfx/src/main/java/org/fxmisc/richtext/model/StyleSpansBuilder.java

@@ -181,7 +181,7 @@ private void _add(StyleSpan<S> span) {
 
     private void ensureNotCreated() {
         if(created) {
-            throw new IllegalStateException("Cannot reus StyleRangesBuilder after StyleRanges have been created.");
+            throw new IllegalStateException("Cannot reuse StyleRangesBuilder after StyleRanges have been created.");
         }
     }
 }
@@ -447,4 +447,4 @@ public StyleSpan<S> getStyleSpan(int index) {
             throw new IndexOutOfBoundsException(String.valueOf(index));
         }
     }
-}
+}