text: Title: Validation doc section "On instantiation" improvement
  Body: I think the example given in the docs here could do with some improvement to make it clearer:
  
  https://github.com/dynaconf/dynaconf/blob/4ab518393a1f7aa72e353a485aebea2852561120/docs/validation.md?plain=1#L36-L58
  
  1. It refers to the example `settings.toml` given in [this section](https://www.dynaconf.com/validation/#overview), so I feel like the example should have `settings_files=["settings.toml"]` and `environments=True` so that a user can easily recreate a working example.
  2. `Path` is imported here but not used
  3. The horizontal whitespace between validators could be taken out
  4. The will raise section at the end could be presented better, and currently it doesn't seem to be accurate because of a potential bug #1068  