feat: expose FeeRate::fee_vb and FeeRate::fee_wu methods

Author: thunderbiscuit

bdk-ffi/src/bitcoin.rs

@@ -30,6 +30,7 @@ use bdk_wallet::bitcoin::Transaction as BdkTransaction;
 use bdk_wallet::bitcoin::TxIn as BdkTxIn;
 use bdk_wallet::bitcoin::TxOut as BdkTxOut;
 use bdk_wallet::bitcoin::Txid as BitcoinTxid;
+use bdk_wallet::bitcoin::Weight;
 use bdk_wallet::bitcoin::Wtxid as BitcoinWtxid;
 use bdk_wallet::miniscript::psbt::PsbtExt;
 use bdk_wallet::serde_json;