servo: Merge #5656 - Updating documentation for virtualbox users (from Jayflux:master)

Source-Repo: https://github.com/servo/servo
Source-Revision: 8ff83e2e591059df90f802c1bb0fddd631314cdb

servo/README.md

@@ -56,6 +56,10 @@ Cross-compilation for Android:
 Pre-installed Android tools are needed. See wiki for
 [details](https://github.com/mozilla/servo/wiki/Building-for-Android)
 
+Using Virtualbox:
+
+If you're running servo on a guest machine, make sure 3D Acceleration is switched off ([#5643](https://github.com/servo/servo/issues/5643))
+
 ## The Rust compiler
 
 Servo uses a snapshot Rust compiler to build itself. This is normally a