Update CHANGELOG

Author: junderw

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 5.1.5
+__added__
+- `Psbt` now has `getFee(): number` for use when all inputs are finalized. It returns the satoshi fee of the transaction. Calling getFee, getFeeRate, or extractTransaction will cache these values so if you call one after the other, the second call will return immediately.
+
 # 5.1.4
 __changed__
 - `Psbt` inputs using segwit scripts can now work with nonWitnessUtxo as well as the original witnessUtxo. The reasoning for this is that nonWitnessUtxo has all the information contained in the witnessUtxo, so rejecting signing even though we have all the info we need is unnecessary. Trying to sign a non-segwit script with a witnessUtxo will still throw an Error as it should.