doc: add missing copyFile change history
Discovered when working to upgrade Electron to Node.js v14.x - the changes in https://github.com/nodejs/node/pull/27044 were semver-major
and thus should likely be added into the change history for those methods.
cc @BridgeAR
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines