Cannot put default value for new settings item

[diginatu]

For example, we added SettingsName setting item and want its default value to be "New Settings".
We can use hole default settings but cannot set default value with holding previous values because of yaml library we using.

old file

config:
- auto_save_to0_slot: false
  user_name_get: false

generated file (once lounch and quit)

config:
- settings_name: ""
  auto_save_to0_slot: false
  user_name_get: false

expected

config:
- settings_name: "New Settings"
  auto_save_to0_slot: false
  user_name_get: false