Our files are up to a decade old, and have churned so much, that the initial author of the file no longer has much meaning.
Furthermore, this will encourage developers to post to the developer group, rather than emailing Googlers (usually me) directly.
* Add annotations to files under core/events
* Add annotations to files under core/interfaces
* Add annotations to files under core/keyboard_nav
* Add annotations to files under core/renderers
* Add annotations to files under core/serialization
* Add annotations to files under core/theme
* Add annotations to files under core/toolbox
* Add annotations to files under core/utils
* Add annotations to files under core
* Migrate core/events/events.js to ES6 const/let
* Migrate core/events/events.js to goog.module
* Migrate core/events/events.js to named requires
* clang-format core/events/events.js
* Migrate Blockly core to use getRecordUndo/setRecordUndo
* Update core/events.js to reflect latest guidance around exporting mutable fields