[safetensors parser] RE_SAFETENSORS_SHARD_FILE (#593)

```ts
const RE_SAFETENSORS_SHARD_FILE = /\d{5}-of-\d{5}\.safetensors$/;
```

is this regex good to detect shard file based on safetensors filename ?

packages/hub/src/lib/parse-safetensors-metadata.ts

@@ -14,6 +14,7 @@ export const SAFETENSORS_INDEX_FILE = "model.safetensors.index.json";
 /// but in some situations safetensors weights have different filenames.
 export const RE_SAFETENSORS_FILE = /\.safetensors$/;
 export const RE_SAFETENSORS_INDEX_FILE = /\.safetensors\.index\.json$/;
+export const RE_SAFETENSORS_SHARD_FILE = /\d{5}-of-\d{5}\.safetensors$/;
 const PARALLEL_DOWNLOADS = 5;
 const MAX_HEADER_LENGTH = 25_000_000;