增加匿名统计开关

app/src/main/java/io/legato/kazusa/constant/PreferKey.kt

@@ -169,6 +169,7 @@ object PreferKey {
     const val readAloudByMediaButton = "readAloudByMediaButton"
     const val showMangaUi = "showMangaUi"
     const val disableMangaScale = "disableMangaScale"
+    const val firebaseEnabled = "firebaseEnabled"
 
     const val cPrimary = "colorPrimary"
     const val cAccent = "colorAccent"