docs: add TAR format

http-gateways/PATH_GATEWAY.md

@@ -153,6 +153,7 @@ For example:
 
 - [application/vnd.ipld.raw](https://www.iana.org/assignments/media-types/application/vnd.ipld.raw) – disables IPLD/IPFS deserialization, requests a verifiable raw block to be returned
 - [application/vnd.ipld.car](https://www.iana.org/assignments/media-types/application/vnd.ipld.car) – disables IPLD/IPFS deserialization, requests a verifiable CAR stream to be returned
+- [application/x-tar](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types) – disables IPLD/IPFS deserialization, requests a TAR archive to be returned
 <!-- TODO: https://github.com/ipfs/go-ipfs/issues/8823
 - application/vnd.ipld.dag-json OR application/json – requests IPLD Data Model representation serialized into [DAG-JSON format](https://ipld.io/docs/codecs/known/dag-json/)
 - application/vnd.ipld.dag-cbor OR application/cbor - requests IPLD Data Model representation serialized into [DAG-CBOR format](https://ipld.io/docs/codecs/known/dag-cbor/)
@@ -220,7 +221,7 @@ Optional, `format=<format>` can be used to request specific response format.
 
 This is a URL-friendly alternative to sending
 `Accept: application/vnd.ipld.<format>` header, see [`Accept`](#accept-request-header)
-for more details.
+for more details. In case of `application/x-tar`, `<format>` is `tar`.
 
 <!-- TODO Planned: https://github.com/ipfs/go-ipfs/issues/8769
 - `selector=<cid>`  can be used for passing a CID with [IPLD selector](https://ipld.io/specs/selectors)