doc: adds release notes for CJ descriptor

Author: knst

doc/release-notes-6835.md

@@ -0,0 +1,21 @@
+Mobile CoinJoin Compatibility
+------------
+
+- Fixed an issue where CoinJoin funds mixed in Dash Android wallet were
+  invisible when importing the mnemonic into Dash Core. Descriptor Wallets now
+  include an additional default descriptor for mobile CoinJoin funds, ensuring
+  seamless wallet migration and complete fund visibility across different
+  Dash wallet implementations.
+
+- This is a breaking change that increases the default number of descriptors
+  from 2 to 3 on mainnet (internal, external, mobile CoinJoin) for newly created
+  descriptor wallets only - existing wallets are unaffected.
+
+
+Updated RPCs
+------------
+
+- The `listdescriptors` RPC now includes an optional coinjoin field to identify
+  CoinJoin descriptors.
+
+(#6835)