[DOCS] Gentoo dependencies. (#226)

Author: evaan

README.md

@@ -14,6 +14,7 @@ sudo pacman -S qemu python python-pip python-wheel # for Arch.
 sudo xbps-install -Su qemu python3 python3-pip # for Void Linux.
 sudo zypper in qemu-tools qemu-kvm qemu-x86 qemu-audio-pa python3-pip # for openSUSE Tumbleweed
 sudo dnf install qemu qemu-img python3 python3-pip # for Fedora
+sudo emerge -a qemu python:3.4 pip # for Gentoo
 ```
 
 ## Step 1