[Doc] Add multiwallet section to release notes

doc/release-notes.md

@@ -48,6 +48,16 @@ Notable Changes
 
 A new init option flag '-blocksdir' will allow one to keep the blockfiles external from the data directory.
 
+#### Multi-wallet support
+
+PIVX Core now supports loading multiple, separate wallets (See [PR 2337](https://github.com/PIVX-Project/PIVX/pull/2337)). The wallets are completely separated, with individual balances, keys and received transactions, and will remain synchronized to the node's current tip.
+
+Multi-wallet is enabled by using more than one `-wallet` argument when starting PIVX client, either on the command line or in the pivx.conf config file.
+
+**In pivx-qt, only the first wallet will be displayed and accessible for creating and signing transactions.** GUI selectable multiple wallets will be supported in a future version. However, even in 6.0 other loaded wallets will remain synchronized to the node's current tip in the background.
+
+!TODO: update after endpoint support and multi-wallet RPC support
+
 #### Disable PoW mining RPC Commands
 
 A new configure flag has been introduced to allow more granular control over weather or not the PoW mining RPC commands are compiled into the wallet. By default they are not. This behavior can be overridden by passing `--enable-mining-rpc` to the `configure` script.