feat: selection_strategy closest (#885)

* Added closest selection_strategy to use default_selection_index initially but prefer highest ranked match when prompt not empty

* Updated supporting documentation to include selection_strategy

lua/telescope/config.lua

@@ -124,7 +124,8 @@ local telescope_defaults = {
     Available options are:
     - "reset" (default)
     - "follow"
-    - "row"]],
+    - "row"
+    - "closest"]],
   },
 
   scroll_strategy = {

lua/telescope/pickers.lua

@@ -1069,6 +1069,12 @@ function Picker:get_result_completor(results_bufnr, find_id, prompt, status_upda
       else
         self:set_selection(self:get_reset_row())
       end
+    elseif selection_strategy == 'closest' then
+      if prompt == "" and self.default_selection_index ~= nil then
+        self:set_selection(self:get_row(self.default_selection_index))
+      else
+        self:set_selection(self:get_reset_row())
+      end
     else
       error('Unknown selection strategy: ' .. selection_strategy)
     end