* Remove support for `stdweb`
* Expunge `stdweb`; make `web-sys` the default
* Mark this change as a breaking change
* Re-insert accidental removal of space
* Use the correct cargo feature syntax
* Re-add some `cfg` attributes
* Remove `web-sys` feature from CI
* Change web backend `event_handler` to without 'static lifetime
* Refactor web runner and fix ControlFlow::Exit not being sticky
* Impl. scaling change event for web-sys backend
* Improve `dpi` docs regarding the web backend
* Add changes to changelog
* Update features.md
The current implementation of the event loop runner has some significant
problems. It can't handle multiple events being emitted at once (for
example, when a keyboard event causes a key input, a text input, and a
modifier change.) It's also relatively easy to introduce bugs for the
different possible control flow states.
The new model separates intentionally emitting a NewEvents (poll
completed, wait completed, init) and emitting a normal event, as well as
providing a method for emitting multiple events in a single call.
