doc: add release note for bitcoin-cli -generate

Author: jonatack

doc/release-notes-19133.md

@@ -0,0 +1,7 @@
+## CLI
+
+A new `bitcoin-cli -generate` command, equivalent to RPC `generatenewaddress`
+followed by `generatetoaddress`, can generate blocks for command line testing
+purposes. This is a client-side version of the
+[former](https://github.com/bitcoin/bitcoin/issues/14299) `generate` RPC. See
+the help for details. (#19133)