Use dark system bars on API 21

Light system bars didn't come around until API 23.

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

ui/src/main/res/values-v21/styles.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="AppTheme" parent="Theme.MaterialComponents.DayNight">
+        <item name="colorPrimary">@color/primary_color</item>
+        <item name="colorOnPrimary">@color/color_control_normal</item>
+        <item name="colorPrimaryDark">@color/primary_color</item>
+        <item name="colorPrimaryVariant">@color/primary_light_color</item>
+        <item name="colorSecondary">@color/secondary_color</item>
+        <item name="colorOnSecondary">@color/secondary_text_color</item>
+        <item name="colorSurface">@color/primary_color</item>
+        <item name="colorOnSurface">@color/color_control_normal</item>
+        <item name="colorBackground">@color/primary_color</item>
+        <item name="colorMultiselectActiveBackground">@color/list_multiselect_background</item>
+        <item name="colorControlNormal">@color/color_control_normal</item>
+        <item name="elevationOverlayColor">@color/primary_light_color</item>
+        <item name="elevationOverlayEnabled">true</item>
+        <item name="android:statusBarColor">#000000</item>
+        <item name="android:navigationBarColor">#000000</item>
+        <item name="android:windowBackground">@color/primary_color</item>
+        <item name="alertDialogTheme">@style/AppTheme.Dialog</item>
+        <item name="materialAlertDialogTheme">@style/AppTheme.Dialog</item>
+        <item name="actionBarPopupTheme">@style/ThemeOverlay.MaterialComponents.ActionBar</item>
+    </style>
+</resources>