Revert removing Fullscreen theme (#7974)

- Is still used by TachiyomiFullscreenDialog

app/src/main/res/anim/fade_in_short.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<alpha xmlns:android="http://schemas.android.com/apk/res/android"
+    android:duration="100"
+    android:fromAlpha="0.0"
+    android:interpolator="@android:interpolator/linear"
+    android:toAlpha="1.0" />

app/src/main/res/anim/fade_out_short.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<alpha xmlns:android="http://schemas.android.com/apk/res/android"
+    android:duration="100"
+    android:fromAlpha="1.0"
+    android:interpolator="@android:interpolator/linear"
+    android:toAlpha="0.0" />

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

@@ -175,6 +175,16 @@
         <item name="cornerSize">@dimen/card_radius</item>
     </style>
 
+    <style name="ThemeOverlay.Tachiyomi.Dialog.Fullscreen" parent="ThemeOverlay.Material3">
+        <item name="android:windowIsFloating">false</item>
+        <item name="android:windowAnimationStyle">@style/Animation.Tachiyomi.Dialog</item>
+    </style>
+
+    <style name="Animation.Tachiyomi.Dialog" parent="Animation.AppCompat.Dialog">
+        <item name="android:windowEnterAnimation">@anim/fade_in_short</item>
+        <item name="android:windowExitAnimation">@anim/fade_out_short</item>
+    </style>
+
     <!--===========-->
     <!--Preferences-->
     <!--===========-->