Feature request: Huggingface tokenizer support

Since world tokenizer training code is not available as far as I know, those of us who need a custom tokenizer train HF tokenizer (pip rwkv package, RWKV-LM trainer and json2binidx_tool all support it).
Currently it doesn't work with ai00_server: 

> [ai00_server::middleware] reload model failed: failed to parse vocabulary: invalid value: expected key to be a number in quotes at line 2 column 3
