Create OpenWrt makefile

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**FEATURE REQUEST**

To easily integrate fibers into our work we should make an OpenWrt makefile for it. As a pure Lua package it should be relatively straightforward - there's lots of examples in our [jng_openwrt_packages](https://github.com/jangala-dev/jng_openwrt_pkgs/) repo (for example lua-lumen and lua-http).

To use LuaJIT all the packages needed are already in OpenWrt's repos/already have been ported. However, if we were to use plain Lua, we will need to port [cffi-lua](https://github.com/q66/cffi-lua). This is a C++ program so will need a slightly more complex makefile. It's worth looking to see how OpenWrt deals with [other Meson packages](https://github.com/search?q=repo%3Aopenwrt%2Fpackages+meson+makefile&type=code). Buiilding cffi-lua on the command line is quite simple, we do so in the devcontainer process in the [repo](https://github.com/jangala-dev/lua-fibers/blob/main/.devcontainer/postCreateCommand.sh)

Compare the lua-lumen and lua-http examples in the jng_openwrt_packages repository, then inspect .devcontainer/postCreateCommand.sh for how cffi-lua is built. Check OpenWrt's handling of Meson packages and determine whether the package can use LuaJIT or needs the cffi-lua port; done means the OpenWrt makefile builds and integrates lua-fibers.

Written by the indexing model from the issue text.