Add descriptor code sample

docs/getting-started.md

@@ -67,3 +67,53 @@ The author of this project strongly believes descriptors will be a big part of t
 technology and tooling of Bitcoin evolves and changes (Schnorr signatures, Taproot, etc).
 
 To learn more, check out the specific [Descriptors section](/descriptors).
+
+The following code shows how to generate a random mnemonic, the extended (and deterministic) keys from that mnemonic and finally the descriptors from the extended private keys.
+
+To be able to run this code, the `bdk` dependency in `Cargo.toml` must be set as follows:
+
+```
+[dependencies]
+bdk = { version = "0.15.0", default-feature = false, features = ["all-keys"] }
+```
+
+```rust
+use bdk::bitcoin::Network;
+use bdk::database::MemoryDatabase;
+use bdk::keys::{DerivableKey, GeneratableKey, GeneratedKey, ExtendedKey, bip39::{Mnemonic, WordCount, Language}};
+use bdk::template::Bip84;
+use bdk::{miniscript, Wallet, KeychainKind};
+
+fn main() {
+    println!("Hello, world!");
+
+    let network = Network::Testnet; // Or this can be Network::Bitcoin, Network::Signet or Network::Regtest
+
+    // Generate fresh mnemonic
+    let mnemonic: GeneratedKey<_, miniscript::Segwitv0> = Mnemonic::generate((WordCount::Words12, Language::English)).unwrap();
+    // Convert mnemonic to string
+    let mnemonic_words = mnemonic.to_string();
+    // Parse a mnemonic
+    let mnemonic  = Mnemonic::parse(&mnemonic_words).unwrap();
+    // Generate the extended key
+    let xkey: ExtendedKey = mnemonic.into_extended_key().unwrap();
+    // Get xprv from the extended key
+    let xprv = xkey.into_xprv(network).unwrap();
+
+    // Create a BDK wallet structure using BIP 84 descriptor ("m/84h/1h/0h/0" and "m/84h/1h/0h/1")
+    let wallet = Wallet::new_offline(
+        Bip84(xprv, KeychainKind::External),
+        Some(Bip84(xprv, KeychainKind::Internal)),
+        network,
+        MemoryDatabase::default(),
+    )
+    .unwrap();
+
+    println!("mnemonic: {}\n\nrecv desc (pub key): {:#?}\n\nchng desc (pub key): {:#?}",
+        mnemonic_words,
+        wallet.get_descriptor_for_keychain(KeychainKind::External).to_string(),
+        wallet.get_descriptor_for_keychain(KeychainKind::Internal).to_string());
+}
+```
+
+More information about each component used in the code can be found in [BDK Documentation](https://docs.rs/bdk/0.15.0/bdk/index.html).