Add CBF documentation to README

Author: febyeji

README.md

@@ -61,7 +61,7 @@ fn main() {
 LDK Node currently comes with a decidedly opinionated set of design choices:
 
 - On-chain data is handled by the integrated [BDK][bdk] wallet.
-- Chain data may currently be sourced from the Bitcoin Core RPC interface, or from an [Electrum][electrum] or [Esplora][esplora] server.
+- Chain data may currently be sourced from the Bitcoin Core RPC interface, from an [Electrum][electrum] or [Esplora][esplora] server, or via [compact block filters (BIP 157)][bip157] when the `cbf` feature is enabled.
 - Wallet and channel state may be persisted to an [SQLite][sqlite] database, to file system, or to a custom back-end to be implemented by the user.
 - Gossip data may be sourced via Lightning's peer-to-peer network or the [Rapid Gossip Sync](https://docs.rs/lightning-rapid-gossip-sync/*/lightning_rapid_gossip_sync/) protocol.
 - Entropy for the Lightning and on-chain wallets may be sourced from raw bytes or a [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki) mnemonic. In addition, LDK Node offers the means to generate and persist the entropy bytes to disk.
@@ -80,6 +80,7 @@ The Minimum Supported Rust Version (MSRV) is currently 1.85.0.
 [bdk]: https://bitcoindevkit.org/
 [electrum]: https://github.com/spesmilo/electrum-protocol
 [esplora]: https://github.com/Blockstream/esplora
+[bip157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki
 [sqlite]: https://sqlite.org/
 [rust]: https://www.rust-lang.org/
 [swift]: https://www.swift.org/