update readme to add phoenixd to list of crates

README.md

@@ -23,6 +23,7 @@ The project is split up into several crates in the `crates/` directory:
     * [**cdk-lnd**](./crates/cdk-lnd/): Lnd Lightning backend for mint.
     * [**cdk-strike**](./crates/cdk-strike/): Strike Lightning backend for mint.
     * [**cdk-lnbits**](./crates/cdk-lnbits/): [LNbits](https://lnbits.com/) Lightning backend for mint.
+    * [**cdk-phoenixd**](./crates/cdk-phoenixd/): Phoenixd Lightning backend for mint.
     * [**cdk-fake-wallet**](./crates/cdk-fake-wallet/): Fake Lightning backend for mint. To be used only for testing, quotes are automatically filled.
 * Binaries:
     * [**cdk-cli**](./crates/cdk-cli/): Cashu wallet CLI.