Update the documentation (#13)

Author: DilumAluthge

README.md

@@ -10,8 +10,6 @@
 ```julia
 julia> using GitRepl
 
-julia> gitrepl() # you only need to run this once per Julia session
-
 # Press , to enter the Git REPL mode
 
 git> clone https://github.com/JuliaRegistries/General

src/GitRepl.jl

@@ -18,6 +18,7 @@ function _gitrepl_parser(repl_input::AbstractString)
 end
 
 """
+    gitrepl()
     gitrepl(; kwargs...)
 
 Set up the Git REPL mode.