Automatically generate screenshots for all examples (#2379)

examples/serial_windows/Cargo.toml

@@ -9,4 +9,6 @@ publish = false
 
 
 [dependencies]
-eframe = { path = "../../crates/eframe" }
+eframe = { path = "../../crates/eframe", features = [
+    "__screenshot", # __screenshot is so we can dump a ascreenshot using EFRAME_SCREENSHOT_TO
+] }

examples/serial_windows/README.md

@@ -6,3 +6,5 @@ See also <https://github.com/emilk/egui/issues/1918>.
 ```sh
 cargo run -p serial_windows
 ```
+
+![](screenshot.png)

examples/serial_windows/src/main.rs

@@ -9,6 +9,7 @@ fn main() {
 
     let options = eframe::NativeOptions {
         run_and_return: true,
+        initial_window_size: Some(egui::vec2(320.0, 240.0)),
         ..Default::default()
     };