* egui_web: use tracing crate
* egui_glow: use tracing crate
* Log at the debug level
* egui_demo_app: enable tracing to log to stdout
* Use tracing in egui-winit
* Add opt-in tracing support to egui
* Re-add check of WEBGL_debug_renderer_info to avoid OpenGL error
I removed this check in https://github.com/emilk/egui/pull/1020
because it produced a warning on Firefox. Better a warning
than an OpenGL error though.
* Bug fix: don't ask for webgl context and then later for webgl2 context
The browser will only allow the first thing we check, so this will
prevent webgl2 from working.
