refactor(tracker): use UnmarshalStrict when decoding embedded yamls

Since we have 100% control over what data gets embedded, there is no
reason to embed anything that doesn't pass the strict yaml parsing
and it's better we throw a panic right away so it's easy to catch
this during development.

tracker/gioui/preferences.go

@@ -29,7 +29,7 @@ var defaultPreferencesYaml []byte
 
 func loadDefaultPreferences() Preferences {
 	var preferences Preferences
-	err := yaml.Unmarshal(defaultPreferencesYaml, &preferences)
+	err := yaml.UnmarshalStrict(defaultPreferencesYaml, &preferences)
 	if err != nil {
 		panic(fmt.Errorf("failed to unmarshal preferences: %w", err))
 	}