text: Title: .secrets.toml not read automatically
  Body: Hi there,
  
  currently I'm evaluating various libraries for settings management in my next project. One favorite is Dynaconf, it relly shines! :)
  One thing which makes me wonder is that according to the docs the file `.secrets.toml` should be automatically read, shouldn't it?
  Example:
  ```
  # conf/myprog.toml
  BASE='/some/path'
  SECRET_KEY='abc123'
  
  # conf/myprog.local.toml
  BASE='/foo/bar'
  
  # conf/.secrets.toml
  SECRET_KEY='wildwilly'
  ```
  Running a normal Python shell I import the settings and showed the result:
  ```
  >>> from dynaconf import Dynaconf
  >>> settings = Dynaconf(root_path='conf', merge_enabled=true, settings_files=['myprog.toml'])
  >>> settings.to_dict()
  {'BASE': '/foo/bar', 'SECRET_KEY': 'abc123'}
  ```
  To my understanding `SECRET_KEY` should be `wildwilly`. So why it is not changed in the result? Or do I have to specify .secrets.toml explicitly in settings_files? Btw, it does not matter, if .secrets.toml is under conf or in the directory above (from where I started the interpreter from).
  
  Dynaconf version is 3.1.5.
  
  Many thanks 