feat: prompt user to save changes before editing moved file/dir (#93)

doc/oil.txt

@@ -45,6 +45,8 @@ OPTIONS                                                              *oil-option
       skip_confirm_for_simple_edits = false,
       -- Deleted files will be removed with the `trash-put` command.
       delete_to_trash = false,
+      -- Selecting a new/moved/renamed file or directory will prompt you to save changes first
+      prompt_save_on_select_new_entry = true,
       -- Keymaps in oil buffer. Can be any value that `vim.keymap.set` accepts OR a table of keymap
       -- options with a `callback` (e.g. { callback = function() ... end, desc = "", nowait = true })
       -- Additionally, if it is a string that matches "actions.<name>",