Update release notes

doc/release-notes.md

@@ -4,6 +4,23 @@ release-notes at release time)
 Notable changes
 ===============
 
+Wallet
+------
+
+From this release, newly-created wallets will save the chain name ("Zcash") and
+network identifier (e.g. "main") to the `wallet.dat` file. This will enable the
+`zcashd` node to check on subsequent starts that the `wallet.dat` file matches
+the node's configuration. Existing wallets will start saving this information in
+a later release.
+
+`libzcash_script`
+-----------------
+
+Two new APIs have been added to this library (`zcash_script_legacy_sigop_count`
+and `zcash_script_legacy_sigop_count_precomputed`), for counting the number of
+signature operations in the transparent inputs and outputs of a transaction.
+The presence of these APIs is indicated by a library API version of 2.
+
 Updated RPCs
 ------------