UI: update splash screen

Author: InfinityLoop1308

app/src/main/res/drawable-night-v23/splash_background.xml

@@ -2,11 +2,11 @@
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
 
     <item
-        android:drawable="@color/dark_youtube_primary_color"/>
+        android:drawable="@color/dark_bilibili_primary_color"/>
 
     <item
         android:width="80dp"
         android:height="80dp"
         android:gravity="center"
-        android:drawable="@drawable/splash_foreground"/>
+        android:drawable="@drawable/ic_pipepipe"/>
 </layer-list>

app/src/main/res/drawable-v23/splash_background.xml

@@ -2,11 +2,11 @@
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
 
     <item
-        android:drawable="@color/light_youtube_primary_color"/>
+        android:drawable="@color/light_bilibili_primary_color"/>
 
     <item
         android:width="80dp"
         android:height="80dp"
         android:gravity="center"
-        android:drawable="@drawable/splash_foreground"/>
+        android:drawable="@drawable/ic_pipepipe"/>
 </layer-list>

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

@@ -2,7 +2,7 @@
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
 
     <item
-        android:drawable="@color/light_youtube_primary_color"/>
+        android:drawable="@color/light_bilibili_primary_color"/>
 
     <item>
         <bitmap