Support stylua

I have stylua installed, but attempting to format a Lua file returns: 

```
Error detected while processing function CocAction[4]..coc#rpc#request[4]..<SNR>9_request[34]..function CocAction[4]..coc#rpc#request[4]..<SNR>
9_request:
line   31:
E605: Exception not caught: Error on request: Vim(return):Error invoking 'format' on channel 4 (coc):^@Format provider not found for buffer: 22
```