Initial release of Gopjrt:

• xlabuilder with good coverage: all ops used by GoMLX.
• pjrt with enough functionality coverage for GoMLX and to execute some Jax functions.
• Documentation for API, examples, one notebook (Mandelbrot) and installation details for CUDA.
• Prebuilt cpu pjrt plugin and C/C++ XlaBuilder libraries for linux/x86-64.