doc: add release notes for explicit fee estimators and bumpfee change
doc: add release notes for explicit fee estimators and bumpfee change

Former-commit-id: a88c6c1c9a7118def19ae61c14d20944621f4b67
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin