doc: add important information about tx flood to release notes
doc: add important information about tx flood to release notes

psionin/smartcoin,koharjidan/dogecoin,koharjidan/dogecoin,psionin/smartcoin,koharjidan/dogecoin,dogecoin/dogecoin,patricklodder/dogecoin,patricklodder/dogecoin,psionin/smartcoin,psionin/smartcoin,dogecoin/dogecoin,psionin/smartcoin,dogecoin/dogecoin,patricklodder/dogecoin,koharjidan/dogecoin,dogecoin/dogecoin,koharjidan/dogecoin,patricklodder/dogecoin,koharjidan/dogecoin,dogecoin/dogecoin,dogecoin/dogecoin,patricklodder/dogecoin,psionin/smartcoin