Add web page for the MNIST example

[rgerganov]

The web page is using WASM for model inference.
Users can draw digits on an HTML canvas and load random digits from the MNIST dataset.

[rgerganov]

Right now I build this with:

cd examples/mnist
emcc -I../../include -I../../include/ggml -I../../examples ../../src/ggml.c main.cpp -o web/mnist.js -s EXPORTED_FUNCTIONS='["_wasm_eval","_wasm_random_digit","_malloc","_free"]' -s EXPORTED_RUNTIME_METHODS='["ccall"]' -s ALLOW_MEMORY_GROWTH=1 --preload-file models/mnist

I need to figure out how to integrate it in the CMake build

[matthoffner]

@rgerganov thanks for your example I was able to get it to build with the starcoder example: https://huggingface.co/spaces/matthoffner/ggml-maker/blob/main/examples/wasm-starcoder.Dockerfile