`@connector` is not documentable

[jonniedie]

In my efforts to abuse the @connector macro to allow multiple dispatch on systems that aren't actually connectors (see #1071), I noticed that you can't add documentation to things that were defined with the macro. Example:

julia> using ModelingToolkit

julia> """
       Hey there
       """
       @connector function Pin(;name)
           sts = @variables v(t)=1.0 i(t)=1.0
           ODESystem(Equation[], t, sts, []; name=name)
       end
ERROR: cannot document the following expression:

#= REPL[5]:4 =# @connector function Pin(; name)
        #= REPL[5]:4 =#
        #= REPL[5]:5 =#
        sts = #= REPL[5]:5 =# @variables(v(t) = begin
                        #= REPL[5]:5 =#
                        1.0
                    end, i(t) = begin
                        #= REPL[5]:5 =#
                        1.0
                    end)
        #= REPL[5]:6 =#
        ODESystem(Equation[], t, sts, []; name = name)
    end

'@connector' not documentable. See 'Base.@__doc__' docs for details.

Stacktrace:
 [1] error(::String, ::String)
   @ Base .\error.jl:42
 [2] top-level scope
   @ REPL[5]:1

[YingboMa]

You can use @doc

julia> Base.@doc "Hello" Pin
Pin

help?> Pin
search: Pin print println pointer printstyled pointer_from_objref sprint isprint typeintersect codepoint atreplinit typemin flipsign unsafe_pointer_to_objref Exception prevind copysign typejoin pipeline ErrorException skipmissing

  Hello