Update for Raspberry Pi 4

The Raspberry Pi 4 was just released, so I edited the topic to include "raspberry-pi-4" as an alias. Also slightly modified the description.

Author: petercunha

topics/raspberry-pi/index.md

@@ -1,13 +1,13 @@
 ---
-aliases: raspberry-pi-3, raspberry-pi-2, raspberry-pi-camera, raspberrypi
+aliases: raspberry-pi-4, raspberry-pi-3, raspberry-pi-2, raspberry-pi-camera, raspberrypi
 created_by: Raspberry Pi Foundation
 display_name: Raspberry Pi
 github_url: https://github.com/raspberrypi
 logo: raspberry-pi.png
 released: July 2011
 short_description: The Raspberry Pi is a popular single-board computer.
 topic: raspberry-pi
-url: https://www.raspberrypi.org/
+url: https://www.raspberrypi.org
 wikipedia_url: https://en.wikipedia.org/wiki/Raspberry_Pi
 ---
-The Raspberry Pi is a popular single-board computer designed to promote the teaching of computer science in schools. The use of the Raspberry Pi computer ranges from robotics to home automation. Many variations of the Raspberry Pi exist, such as the Raspberry Pi Zero, which is smaller than the more powerful Raspberry Pi 3.
+The Raspberry Pi is a popular single-board computer designed to promote the teaching of computer science in schools. The use of the Raspberry Pi computer ranges from robotics to home automation. Many variations of the Raspberry Pi exist, such as the Raspberry Pi Zero, which is smaller than the more powerful Raspberry Pi 4.