Final 'Release Notes' and 'Upgrading' for 3.4.0.

Author: carlosame

RELEASE_NOTES.txt

@@ -2,7 +2,7 @@
                             CSS4J RELEASE NOTES
                             ===================
 
-Release 3.4.0 - February 26, 2021
+Release 3.4.0 - February 28, 2021
 ---------------------------------
 
 Release Highlights

UPGRADING.txt

@@ -14,7 +14,8 @@ Upgrading to 3.4 from 3.3
    returns a new DeclarationFormattingContext.
  - Removed method newLine(SimpleWriter) from DeclarationFormattingContext
    interface.
- - NSAC only: new method CSSHandler.lexicalProperty(...).
+ - NSAC only: new method CSSHandler.lexicalProperty(...). For now, only being
+   called for one descriptor from @property rules.
 
 
 Upgrading to 3.3 from 3.2