Combine demo_glium and demo_web into one egui_demo crate

egui_demo/src/lib.rs

@@ -0,0 +1,18 @@
+#![forbid(unsafe_code)]
+#![cfg_attr(not(debug_assertions), deny(warnings))] // Forbid warnings in release builds
+#![warn(clippy::all)]
+
+#[cfg(target_arch = "wasm32")]
+use wasm_bindgen::prelude::*;
+
+/// This is the entry-point for all the web-assembly.
+/// This is called once from the HTML.
+/// It loads the app, installs some callbacks, then returns.
+/// You can add more callbacks like this if you want to call in to your code.
+#[cfg(target_arch = "wasm32")]
+#[wasm_bindgen]
+pub fn start(canvas_id: &str) -> Result<(), wasm_bindgen::JsValue> {
+    let app = egui::DemoApp::default();
+    egui_web::start(canvas_id, Box::new(app))?;
+    Ok(())
+}

egui_demo/src/main.rs

@@ -0,0 +1,9 @@
+#![forbid(unsafe_code)]
+#![cfg_attr(not(debug_assertions), deny(warnings))] // Forbid warnings in release builds
+#![warn(clippy::all)]
+
+// When compiling natively:
+fn main() {
+    let app = egui::DemoApp::default();
+    egui_glium::run(Box::new(app));
+}