feat: add information on the features supported by the public IPFS gateways

Author: aschmahmann

docs/concepts/public-utilities.md

@@ -34,6 +34,29 @@ From there, an internal system extracts the relevant information from the reques
 
 Your browser may have a local cache of the content in question and might not reflect that something has been blocked on the gateways. To avoid browser caching, attempt to view the content using your browser's incognito or private mode. You can also prevent caching issues by using a command-line tool such as Curl or Wget.
 
+### Supported Features
+
+IPFS implementations can support a variety of protocols and specifications. The above public gateways support the following:
+
+- ipfs.io and dweb.link support the full set of IPFS Gateway specifications: https://specs.ipfs.tech/http-gateways/
+- trustless-gateway.link supports only the Trustless Gateway subset: https://specs.ipfs.tech/http-gateways/trustless-gateway/
+
+They support HTTP clients reaching them over both ipv4 and ipv6 addresses
+
+The underlying IPFS nodes backing the gateways support the following mutable identifiers under the `/ipns` namespace:
+- IPNS Public Keys
+- DNSLink for all IANA registered domains as well as .crypto and .eth
+
+The underlying IPFS nodes backing the gateways support retrieving data from peers that:
+- Have either ipv4 or ipv6 addresses
+- Are either reachable over the public internet or are accessible via libp2p's relay-v2 protocol and reach out to the gateway nodes via dialback
+- Support one of the following libp2p transport configurations:
+   - QUIC-v1
+   - TCP or WS or WSS, Yamux, TLS or Noise
+   - WebTransport
+- Support the Bitswap protocol (any versions 1 through 1.2)
+- Have either advertised their data to the Amino DHT, or have advertised to IPNI such that their data has been indexed by cid.contact
+
 ## Other Public Gateways
 
 Additionally, there's a community-maintained [tool for finding and testing public gateways](https://ipfs.github.io/public-gateway-checker/).