[FEATURE] Add Naïve forecasting benchmark

[rasyidstat]

Description

A simple Naïve forecasting benchmark in R and Python

Expected behavior with the suggested feature

Help people to get a quick and simple benchmark in forecasting

[vapaunic]

Hi, thanks for the suggestion. Just to clarify, you're suggesting we include a Naive model to the R and Python examples? We do already have a Naive model under R examples in this example: https://github.com/microsoft/forecasting/blob/master/examples/grocery_sales/R/02_basic_models.Rmd

Is this what you had in mind?

[rasyidstat]

Sorry, I did not see it. I think that we need to add Naïve model to the documentation then.