Add demo app instructions for Defora Rawhide

Closes https://github.com/emilk/egui/issues/235

README.md

@@ -44,9 +44,11 @@ To test the demo app locally, run `cargo run --release -p egui_demo_app`.
 
 The native backend is currently using [`glium`](https://github.com/glium/glium) ([though there are plans to change that](https://github.com/emilk/egui/issues/93)) and should work out-of-the-box on Mac and Windows, but on Linux you need to first run:
 
-`sudo apt-get install libxcb-render0-dev libxcb-shape0-dev libxcb-xfixes0-dev`
+`sudo apt-get install libxcb-render0-dev libxcb-shape0-dev libxcb-xfixes0-dev libspeechd-dev`
 
-**NOTE**: egui itself is completely platform agnostic.
+On Fedora Rawhide you need to run `dnf install clang clang-devel clang-tools-extra speech-dispatcher-devel`
+
+**NOTE**: This is just for the demo app - egui itself is completely platform agnostic!
 
 ### Example