Some documentation to build egui demo app on Fedora Rawhide

```
rustup update
dnf install clang clang-devel clang-tools-extra speech-dispatcher-devel
git clone https://github.com/emilk/egui.git
cd egui/egui_demo_app/
cargo build --release --all-features
cd ..
./target/release/egui_demo_app
```
