[tokbench](https://github.com/huggingface/tokbench)'s `make models` downloads `models/<name>/tokenizer.json` for its five benchmark models from this dataset. None of those paths exist yet, so a fresh clone fails at `make models`. This PR adds them.

Each file is the unmodified `tokenizer.json` from the official model repo (full vocabularies — all five pass tokbench's truncated-vocab check, and the full benchmark matrix was run locally against these exact files before opening this PR):

| path | source | revision | sha256 |
|---|---|---|---|
| `models/gpt2/tokenizer.json` | [openai-community/gpt2](https://huggingface.co/openai-community/gpt2) | `607a30d783df` | `8414cab924d8b9b3…` |
| `models/llama-3/tokenizer.json` | [meta-llama/Meta-Llama-3-8B](https://huggingface.co/meta-llama/Meta-Llama-3-8B) | `8cde5ca83804` | `e134af98b985517b…` |
| `models/deepseek-v4/tokenizer.json` | [deepseek-ai/DeepSeek-V4-Pro](https://huggingface.co/deepseek-ai/DeepSeek-V4-Pro) | `b5968e9190ef` | `8f9f37ca37fdc4f5…` |
| `models/bert-base-uncased/tokenizer.json` | [google-bert/bert-base-uncased](https://huggingface.co/google-bert/bert-base-uncased) | `86b5e0934494` | `ce64fce797c24f68…` |
| `models/t5-base/tokenizer.json` | [google-t5/t5-base](https://huggingface.co/google-t5/t5-base) | `a9723ea7f1b3` | `d2acde0d8d71dd30…` |

Notes:
- `deepseek-v4`: DeepSeek-V4-Pro and DeepSeek-V4-Flash serve a byte-identical tokenizer.json (same LFS object), so one file covers the family.
- `llama-3`: taken from the gated meta-llama/Meta-Llama-3-8B repo rather than reusing the root-level `llama-3-tokenizer.json` already in this dataset, because that file is a **Llama-3.1** config: same 128000-entry vocab and identical merges, but ids 128004/128008/128010 hold `<|finetune_right_pad_id|>` / `<|eom_id|>` / `<|python_tag|>` where Llama-3 has `<|reserved_special_token_*|>`. tokbench names this model `llama-3` and renders its chat fixtures from the Llama-3 (not 3.1) template, so the Llama-3 config is the consistent choice. With the current fixture set the two are interchangeable anyway — no fixture contains any of the differing special tokens.