Example added for Agent.update/4 (#9172)
Example added for Agent.update/4 (#9172)


lexmag/elixir,elixir-lang/elixir,kimshrier/elixir,ggcampinho/elixir,michalmuskala/elixir,kelvinst/elixir,pedrosnk/elixir,kelvinst/elixir,lexmag/elixir,ggcampinho/elixir,pedrosnk/elixir,kimshrier/elixir,joshprice/elixir