Update changelog

Author: Bentroen

datafiles/Data/changelog.txt

@@ -20,6 +20,7 @@ Changes in v3.9.2 (2021.XX.XX):
    multiple of 0.25.
    * Fixed data packs playing wrong notes (or not playing at all) when pitch
    changes cause a note to cross the out-of-range boundary.
+   * Fixed the data pack visualizer using incorrect blocks.
    * Fixed the 'Reset' button appearing in Song stats when using the player
       mode.
    * Fixed the song work stats being updated while using the player mode.
@@ -53,6 +54,8 @@ Changes in v3.9.2 (2021.XX.XX):
       Preferences.
    * Fixed the GitHub and Website button links being switched in the About
       window.
+   * Improved performance when drawing multi-language text.
+   * Improved performance slightly when many notes are displayed on screen.
    * Improved wording in the Edit menu and the Compatibility window.
 
 Changes in v3.9.1 (2021.09.25):