add nginx-lua

[aogg]

[rltas]

Would be easy if you could just install the module, but the config doesn't read snippets from the modules dir, so you have to do something like this on alpine:

RUN apk add --no-cache nginx-mod-http-lua \
    && sed -i '5i \
    load_module /usr/lib/nginx/modules/ndk_http_module.so; \
    load_module /usr/lib/nginx/modules/ngx_http_lua_module.so; \
    pcre_jit on; \
    ' /opt/docker/etc/nginx/nginx.conf