Add GPUArrays.jl and Metal.jl examples in README (#49)

Author: giordano

README.md

@@ -74,7 +74,9 @@ runtests(MyModule, ARGS; init_code)
 There are a few packages already using `ParallelTestRunner.jl` to parallelize their tests, you can look at their setups if you need inspiration to move your packages as well:
 
 * [`Enzyme.jl`](https://github.com/EnzymeAD/Enzyme.jl/blob/main/test/runtests.jl)
+* [`GPUArrays.jl`](https://github.com/JuliaGPU/GPUArrays.jl/blob/master/test/runtests.jl)
 * [`GPUCompiler.jl`](https://github.com/JuliaGPU/GPUCompiler.jl/blob/master/test/runtests.jl)
+* [`Metal.jl`](https://github.com/JuliaGPU/Metal.jl/blob/main/test/runtests.jl)
 
 ## Inspiration
 Based on [@maleadt](https://github.com/maleadt) test infrastructure for [CUDA.jl](https://github.com/JuliaGPU/CUDA.jl).