add auto update subscriptions with interval

V2rayNG/app/src/main/res/layout/activity_sub_edit.xml

@@ -94,6 +94,28 @@
 
             </LinearLayout>
 
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="@dimen/layout_margin_top_height"
+                android:orientation="horizontal">
+
+                <TextView
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1.0"
+                    android:text="@string/sub_auto_update" />
+
+
+                <androidx.appcompat.widget.AppCompatCheckBox
+                    android:id="@+id/auto_update_check"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:paddingStart="2dp"
+                    android:paddingEnd="6dp" />
+
+            </LinearLayout>
+
         </LinearLayout>
 
         <LinearLayout

V2rayNG/app/src/main/res/values/strings.xml

@@ -183,6 +183,7 @@
     <string name="sub_setting_remarks">remarks</string>
     <string name="sub_setting_url">Optional URL</string>
     <string name="sub_setting_enable">enable update</string>
+    <string name="sub_auto_update">Auto update</string>
     <string name="title_sub_update">Update subscription</string>
     <string name="title_ping_all_server">Tcping all configuration</string>
     <string name="title_real_ping_all_server">Real delay all configuration</string>

V2rayNG/app/src/main/res/xml/pref_settings.xml

@@ -126,6 +126,21 @@
 
     </PreferenceCategory>
 
+    <PreferenceCategory android:title="Subscription">
+
+        <CheckBoxPreference
+            android:key="pref_auto_update_subscription"
+            android:summary="Update your subscriptions automatically with an interval in background"
+            android:title="Automatic update subscriptions" />
+
+        <EditTextPreference
+            android:key="pref_auto_update_interval"
+            android:summary="1440 min"
+            android:inputType="number"
+            android:title="Subscription Update Interval (Minutes)" />
+
+    </PreferenceCategory>
+
     <PreferenceCategory android:title="@string/title_ui_settings">
 
         <CheckBoxPreference