eframe web: detect and report panics during startup (#2992)

* Detect panics during initialization and show them to the user

* PanicHandler now also logs the panics

* Add example of how to call into your app from JS

* Refactor: break out AppRunner and AppRunnerRef to own files

* Hide AppRunner

* Simplify user code

* AppRunnerRef -> WebRunner

* Better docs

* Don't paint until first animation frame

* Update multiple_apps.html

* Update web demo

* Cleanup and fixes

* left-align panic message in html

Cargo.lock

@@ -789,16 +789,6 @@ dependencies = [
  "env_logger",
 ]
 
-[[package]]
-name = "console_error_panic_hook"
-version = "0.1.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a06aeb73f470f66dcdbf7223caeebb85984942f22f1adb2a088cf9668146bbbc"
-dependencies = [
- "cfg-if",
- "wasm-bindgen",
-]
-
 [[package]]
 name = "core-foundation"
 version = "0.9.3"
@@ -1281,7 +1271,6 @@ version = "0.21.0"
 dependencies = [
  "bytemuck",
  "chrono",
- "console_error_panic_hook",
  "eframe",
  "egui",
  "egui_demo_lib",