feat: added autoclose functionality

doc/symbols-outline.txt

@@ -49,6 +49,7 @@ or skip this section entirely if you want to roll with the defaults.
         auto_preview = true,
         position = 'right',
         width = 25,
+        auto_close = false,
         show_numbers = false,
         show_relative_numbers = false,
         show_symbol_details = true,
@@ -132,6 +133,15 @@ width
 
     Type: int
 
+-----------------------------------------------------------------------------
+auto_close
+
+    Whether to automatically close the window after selection
+
+    Default: false                                                         ~
+
+    Type: boolean
+
 -----------------------------------------------------------------------------
 auto_preview