Add changelog item

Author: gumb0

CHANGELOG.md

@@ -21,6 +21,7 @@
 - Added: [#5705](https://github.com/ethereum/aleth/pull/5705) Istanbul support: EIP 1108 Reduce alt_bn128 precompile gas costs.
 - Added: [#5707](https://github.com/ethereum/aleth/pull/5707) Aleth waits for 2 seconds after sending disconnect to peer before closing socket.
 - Added: [#5751](https://github.com/ethereum/aleth/pull/5751) Istanbul support: EIP-152 Add BLAKE2 compression function `F` precompile.
+- Added: [#5758](https://github.com/ethereum/aleth/pull/5758) Istanbul support: activation in Ropsten config.
 - Changed: [#5532](https://github.com/ethereum/aleth/pull/5532) The leveldb is upgraded to 1.22. This is breaking change on Windows and the old databases are not compatible.
 - Changed: [#5559](https://github.com/ethereum/aleth/pull/5559) Update peer validation error messages.
 - Changed: [#5568](https://github.com/ethereum/aleth/pull/5568) Improve rlpx handshake log messages and create new rlpx log channel.