Update changelog

Author: Rahix

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to the `Serial Monitor` crate will be documented in this fil
 * Releases are now linked to libssl 3.4.1 on linux (built on Ubuntu 22.04)
 * allow to plot only every n-th point (max points is 5000, if dataset is larger, it will reduce it by showing only every
   2nd point. if it is larger than 10000 only every 3rd point etc...)
+* Fixed the theme preference setting not being properly restored after restarting the application
 
 ## 0.3.4