Add changelog for diagnostics app

Author: simolus3

.changeset/grumpy-kangaroos-march.md

@@ -4,6 +4,7 @@
 '@powersync/react-native': patch
 '@powersync/web': patch
 '@powersync/common': patch
+'@powersync/diagnostics-app': patch
 ---
 
 Update core extension to 0.4.5