Fix print_script for 1.10 (#36)

* Fix print_script for 1.10

Appearantly, at the time when @generated is evaluated, methods from
other packages may not have been compiled yet, so
`hasmethod(show, Tuple{IO, MIME{Symbol("text/javascript")}, value})`
returns false, and the @generated function print_script throws an error.

As the old version worked in 1.9.3, this appears to be the result of
subtle changes in precompilation/initialization
behavior somewhere between 1.9.3 and 1.10.0-beta2.

* Add version discriminator for print_script(::IO, ::MIME,::Any)
Keep the old behavior (via @generated) for versions <=1.9.x.

src/script.jl

@@ -95,20 +95,28 @@ The fallback behavior of `print_script` is to show the object as
 `"text/javascript"`. The `Javascript` wrapper will take any string
 and let it be printed in this way.
 """
+@static if VERSION > v"1.9.99"
+    # With the new JuliaSyntax parser, `hasmethod` appears to be invoked before
+    # other packages are loaded. 
+    print_script(io::IO, value::Any) =
+        show(io, MIME"text/javascript"(), value)
+else
 @generated function print_script(io::IO, value)
      # workaround for Julia#18221
      if hasmethod(show, Tuple{IO, MIME{Symbol("text/javascript")}, value})
          return :(show(io, MIME"text/javascript"(), value))
      end
      throw("$(value) is not showable as text/javascript")
 end
+end
 print_script(io::IO, ::Nothing) =
     print(io, "undefined")
 print_script(io::IO, ::Missing) =
     print(io, "null")
 print_script(io::IO, value::Union{Bool, Symbol}) =
     print(io, value)
 
+
 function print_script(io::IO, value::Union{NamedTuple, AbstractDict})
     print(io, '{')
     first = true