Add @spec for `main` in escript
Add @spec for `main` in escript

Signed-off-by: Mikhail S. Pobolovets <4a7321ca49ee84ca20631d03da5e994635b62455@gmail.com>

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