fix type check on 2 args json

[disberd]

I started trying out this package to interact with the GitLab API on a self-hosted instance and encountered an error when trying to use the 2 argument @json macro to add things endpoints and types to the GitLabAPI.

I believe the type check in the 2 argument @json macro is wrong, as the APIs seems to be of type Forge rather than ForgeType.

This is based on the 1 argument definition of @json (which calls the same 2-argument function json as the 2-argument macro):

GitForge.jl/src/helpers.jl

Lines 21 to 28 in f8df114

	macro json(def::Expr)
	forge = try
	getfield(__module__, Symbol(string(nameof(__module__)) * "API"))
	catch
	throw("No forge struct named $forge. Make one or pass $(__module__)'s forge struct to @json $(def.args[2])")
	end
	json(forge, def)
	end

which simply extracts the struct $(ModuleName)API which always seems of type Forge rather than ForgeType:

• GitForge.jl/src/forges/GitLab/GitLab.jl

  Line 83 in f8df114

  struct GitLabAPI <: Forge

• GitForge.jl/src/forges/GitHub/GitHub.jl

  Line 79 in f8df114

  struct GitHubAPI <: Forge

[disberd]

@christopher-dG, could check if this can be merged or point me to someone else for review?