docs: add xclip installation for fedora (dnf) (#82)

README.md

@@ -48,6 +48,7 @@ On Linux, clipboard support requires:
 - `xclip` or `xsel` for X11.
   - Ubuntu: `apt install xclip`
   - Arch Linux: `pacman -S xclip`
+  - Fedora: `dnf install xclip`
 - `wl-clipboard` for Wayland.
 
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