Fix some sheet color issues (closes #3000)

app/src/main/res/layout/reader_page_sheet.xml

@@ -20,13 +20,14 @@
             android:layout_width="24dp"
             android:layout_height="24dp"
             app:srcCompat="@drawable/ic_photo_24dp"
-            app:tint="@color/md_white_1000_54" />
+            app:tint="?attr/colorOnBackground" />
 
         <TextView
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:layout_marginStart="32dp"
-            android:text="@string/set_as_cover" />
+            android:text="@string/set_as_cover"
+            android:textColor="?attr/colorOnBackground" />
 
     </LinearLayout>
 
@@ -45,13 +46,14 @@
             android:layout_width="24dp"
             android:layout_height="24dp"
             app:srcCompat="@drawable/ic_share_24dp"
-            app:tint="@color/md_white_1000_54" />
+            app:tint="?attr/colorOnBackground" />
 
         <TextView
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:layout_marginStart="32dp"
-            android:text="@string/action_share" />
+            android:text="@string/action_share"
+            android:textColor="?attr/colorOnBackground" />
 
     </LinearLayout>
 
@@ -70,13 +72,14 @@
             android:layout_width="24dp"
             android:layout_height="24dp"
             app:srcCompat="@drawable/ic_file_download_black_24dp"
-            app:tint="@color/md_white_1000_54" />
+            app:tint="?attr/colorOnBackground" />
 
         <TextView
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:layout_marginStart="32dp"
-            android:text="@string/action_save" />
+            android:text="@string/action_save"
+            android:textColor="?attr/colorOnBackground" />
 
     </LinearLayout>
 

app/src/main/res/layout/source_filter_sheet.xml

@@ -8,7 +8,7 @@
     <androidx.constraintlayout.widget.ConstraintLayout
         android:layout_width="match_parent"
         android:layout_height="?attr/actionBarSize"
-        android:background="?attr/colorPrimary"
+        android:background="?attr/colorSurface"
         android:elevation="2dp"
         android:gravity="center"
         android:paddingStart="?attr/listPreferredItemPaddingStart"
@@ -24,7 +24,7 @@
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toTopOf="parent"
-            app:tint="?attr/colorOnBackground" />
+            app:tint="?attr/colorOnSurface" />
 
         <Button
             android:id="@+id/reset_btn"