fix a language code block (#40)

Author: KristofferC

README.md

@@ -67,7 +67,7 @@ julia> signatures_at("/home/tim/.julia/packages/ColorTypes/BsAWO/src/traits.jl",
 
 CodeTracking also helps correcting for [Julia issue #26314](https://github.com/JuliaLang/julia/issues/26314):
 
-```
+```julia
 julia> @which uuid1()
 uuid1() in UUIDs at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.1\UUIDs\src\UUIDs.jl:50