Write custom luac parser

To write a custom parser for metaworm's luadec, you should

1. Export a function as name parse like this, which parse the binary luac into LuaBytecode struct, and invoke its to_msgpack method to convert to uniform serialized style

use extism_pdk::*;

#[plugin_fn]
pub fn parse(luac: Vec<u8>) -> FnResult<Vec<u8>> {
    parse_(&luac)
        .map_err(|e| WithReturnCode::from(e))?
        .to_msgpack()
        .map_err(|e| WithReturnCode::from(e))
}

2. Build it as WASM cargo b -r --target wasm32-unknown-unknown and load it to decompiler

Refer to this repo: https://github.com/metaworm/openwrt-luac-parser