update shadow colours on daerk theme

Author: ButchersBoy

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Dark.xaml

@@ -15,10 +15,10 @@
     <SolidColorBrush x:Key="MaterialDesignDivider" Color="#616161" />
     <SolidColorBrush x:Key="MaterialDesignSelection" Color="#757575" />
 
-    <Color x:Key="MaterialDesignShadow1">#CCCCCC</Color>
-    <Color x:Key="MaterialDesignShadow2">#C4C4C4</Color>
-    <Color x:Key="MaterialDesignShadow3">#BBBBBB</Color>
-    <Color x:Key="MaterialDesignShadow4">#BBBBBB</Color>
-    <Color x:Key="MaterialDesignShadow5">#BBBBBB</Color>
+    <Color x:Key="MaterialDesignShadow1">#AA000000</Color>
+    <Color x:Key="MaterialDesignShadow2">#AA000000</Color>
+    <Color x:Key="MaterialDesignShadow3">#AA000000</Color>
+    <Color x:Key="MaterialDesignShadow4">#AA000000</Color>
+    <Color x:Key="MaterialDesignShadow5">#AA000000</Color>
 
 </ResourceDictionary>