feat (docs): add WASI-NN GGML HIP backend documentation

[ZORDxDD]

This pull request introduces documentation for building and using the WasmEdge WASI-NN plugin with HIP backend support for AMD GPUs.

The docs refer to the the PR #4309 of the WasmEdge/wasmedge repo which solves the issue #4037

Key additions include:

Prerequisites for using the HIP backend.
Installation instructions for ROCm/HIP.
Steps to build WasmEdge with HIP support.
Configuration options for the HIP backend.
This documentation is added to the existing wasi_nn.md file under the llama.cpp backend section.

[juntao]

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Commit a51a76cc92ed116eaa6583c5178640bbd8e620ab

• The patch introduces documentation for adding a WASI-NN GGML HIP backend to the Wasmedge project. It explains prerequisites, installation steps for AMD GPUs with ROCm/HIP, and configuration options for building the plugin.

Documentation Changes

• Ubuntu/Debian: Added instructions for installing ROCm/HIP, setting up environment variables, and building with Hip support.
• Windows: Provided documentation on building the Wasmedge plugin with llama.cpp backend.

[hydai]

Blocked by WasmEdge/WasmEdge#4309