Dark mode splash screen (closes #2540)

app/src/main/res/drawable/splash_background.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
 
-    <item android:drawable="@color/splashBackgroundColor" />
+    <item android:drawable="?attr/colorBackgroundSplash" />
 
     <item>
         <bitmap

app/src/main/res/values-night/themes.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+
+    <!--===============-->
+    <!-- Launch Screen -->
+    <!--===============-->
+    <style name="Theme.Splash" parent="Theme.Tachiyomi">
+        <item name="colorBackgroundSplash">@color/colorDarkPrimaryDark</item>
+
+        <item name="android:windowBackground">@drawable/splash_background</item>
+        <item name="android:statusBarColor">?attr/colorBackgroundSplash</item>
+        <item name="android:navigationBarColor">?attr/colorBackgroundSplash</item>
+    </style>
+
+</resources>

app/src/main/res/values/attrs.xml

@@ -25,5 +25,7 @@
     <attr name="selectable_library_drawable" format="reference|integer"/>
     <attr name="text_color_primary" format="reference|integer"/>
     <attr name="background_card" format="reference|integer"/>
+    <attr name="colorBackgroundSplash" format="reference|integer"/>
     <attr name="icon_color" format="reference|integer"/>
+
 </resources>

app/src/main/res/values/themes.xml

@@ -161,9 +161,11 @@
     <!-- Launch Screen -->
     <!--===============-->
     <style name="Theme.Splash" parent="Theme.Tachiyomi">
+        <item name="colorBackgroundSplash">@color/colorPrimary</item>
+
         <item name="android:windowBackground">@drawable/splash_background</item>
-        <item name="android:statusBarColor">@color/splashBackgroundColor</item>
-        <item name="android:navigationBarColor">@color/splashBackgroundColor</item>
+        <item name="android:statusBarColor">?attr/colorBackgroundSplash</item>
+        <item name="android:navigationBarColor">?attr/colorBackgroundSplash</item>
     </style>