There are no implementations yet but the usage pattern will be something
like:

```javascript
// unixfs cat command
export async function * cat (cid: CID, blockstore: Blocks, options: Partial<CatOptions> = {}): AsyncIterable<Uint8Array> {
  // create a session for the CID if support is available
  const blocks = await (blockstore.createSession != null ? blockstore.createSession(cid) : blockstore)
  const opts: CatOptions = mergeOptions(defaultOptions, options)

  // resolve and export using the session, if created, otherwise fall back to regular blockstore access
  const resolved = await resolve(cid, opts.path, blocks, opts)
  const result = await exporter(resolved.cid, blocks, opts)

  if (result.type !== 'file' && result.type !== 'raw') {
    throw new NotAFileError()
  }

  if (result.content == null) {
    throw new NoContentError()
  }

  yield * result.content(opts)
}
```

Adds a `@helia/bitswap` module with code ported from `ipfs-bitswap`
and greatly simplified.

- Supports sessions
- Only supports bitswap 1.2.0
- Uses libp2p's metrics system instead of a custom version

…ith-sessions

…ifferent metadata

…ith-sessions

…ith-sessions

Co-authored-by: Russell Dempsey <1173416+SgtPooki@users.noreply.github.com>

Co-authored-by: Russell Dempsey <1173416+SgtPooki@users.noreply.github.com>

…interface

…ith-sessions

…-sessions