Update README.md

Library/macOSRichTextEditor/Source/RichTextEditor.m

@@ -1189,7 +1189,7 @@ typedef NS_ENUM(NSInteger, ParagraphIndentation) {
         NSString *checkString = self.BULLET_STRING;
         if (checkString.length > 1) {
             // chop off last letter and use that
-            checkString = [checkString substringToIndex:[checkString length]-1];
+            checkString = [checkString substringToIndex:checkString.length - 1];
         }
         //else return;
         NSUInteger checkStringLength = [checkString length];

README.md

@@ -27,6 +27,10 @@ This library is based upon Deadpikle's [iOS Rich Text Editor](https://github.com
 - Paragraph indent/outdent
 - Bulleted lists
 
+### Compatibility
+
+The rich text editor is compatible with macOS 10.10+. It might work on older versions, but this has not been tested.
+
 #### Keyboard Shortcuts
 
 | Shortcut  | Action |