Add @ guide for custom shortcut

Author: VictoriousRaptor

Flow.Launcher/CustomShortcutSetting.xaml

@@ -75,6 +75,12 @@
                         Text="{DynamicResource customeQueryShortcutTips}"
                         TextAlignment="Left"
                         TextWrapping="WrapWithOverflow" />
+                    <TextBlock
+                        Margin="0,20,0,0"
+                        FontSize="14"
+                        Text="{DynamicResource customeQueryShortcutGuide}"
+                        TextAlignment="Left"
+                        TextWrapping="WrapWithOverflow" />
                     <Image
                         Width="478"
                         Margin="0,20,0,0"

Flow.Launcher/Languages/en.xaml

@@ -289,6 +289,8 @@
     <!--  Custom Query Shortcut Dialog  -->
     <system:String x:Key="customeQueryShortcutTitle">Custom Query Shortcut</system:String>
     <system:String x:Key="customeQueryShortcutTips">Enter a shortcut that automatically expands to the specified query.</system:String>
+    <system:String x:Key="customeQueryShortcutGuide" xml:space="preserve">A shortcut is expanded when it exactly matches the query. &#10;&#10;If you add an '@' prefix while inputting a shortcut, it matches any position in the query. Builtin shortcuts match any position in a query.
+    </system:String>
     <system:String x:Key="duplicateShortcut">Shortcut already exists, please enter a new Shortcut or edit the existing one.</system:String>
     <system:String x:Key="emptyShortcut">Shortcut and/or its expansion is empty.</system:String>