Update virtualbox documentation to show which versions of VirtualBox are

officially supported by Apertis for each release.

content/guides/virtualbox.md

 +++
 date = "2020-06-09"
+lastmod = "2021-02-03"
 weight = 100
 
 title = "VirtualBox"
@@ -54,16 +55,34 @@ Technology is enabled in BIOS settings.
 
 ## Software
 
-- Windows/Linux/Mac OS
-- Oracle VirtualBox, version 5.0.12 or above (installed in next step)
+- Windows OS
+- Oracle VirtualBox. See supported version and installation instructions below.
+
+### VirtualBox supported version
+
+{{% notice warning %}}
+While you can use VirtualBox in other environments, and even use other
+virtualization solutions, the supported setup is to run VirtualBox on 
+Microsoft Windows.
+{{{% /notice %}}
+
+The following table contains the supported version of VirtualBox and VirtualBox Guest additions for each release of Apertis:
+
+| Apertis release | VirtualBox supported version | VirtualBox_Guest_Additions version |
+| ------ | ------ |
+| v2019 | [6.1.12 r139181 (Qt5.6.2)](https://download.virtualbox.org/virtualbox/6.1.12/VirtualBox-6.1.12-139181-Win.exe) | [6.1.12](https://download.virtualbox.org/virtualbox/6.1.12/VBoxGuestAdditions_6.1.12.iso) |
+| v2020 | [6.1.12 r139181 (Qt5.6.2)](https://download.virtualbox.org/virtualbox/6.1.12/VirtualBox-6.1.12-139181-Win.exe) | [6.1.12](https://download.virtualbox.org/virtualbox/6.1.12/VBoxGuestAdditions_6.1.12.iso) |
+| v2021 | [6.1.12 r139181 (Qt5.6.2)](https://download.virtualbox.org/virtualbox/6.1.12/VirtualBox-6.1.12-139181-Win.exe) | [6.1.12](https://download.virtualbox.org/virtualbox/6.1.12/VBoxGuestAdditions_6.1.12.iso) |
+| v2022 | [6.1.12 r139181 (Qt5.6.2)](https://download.virtualbox.org/virtualbox/6.1.12/VirtualBox-6.1.12-139181-Win.exe) | [6.1.12](https://download.virtualbox.org/virtualbox/6.1.12/VBoxGuestAdditions_6.1.12.iso) |
 
 # Installing VirtualBox
 
 If you have not yet installed Oracle VM VirtualBox, to install the current version of this software, please follow these steps:
 
-- [Download](https://www.virtualbox.org/wiki/Downloads) the most recent version
-  of the VirtualBox installation file for your host platform. Apertis recommend
-  version 5.0.12 or above.
+- [Download](https://www.virtualbox.org/wiki/Downloads) the required version of
+  the VirtualBox installation file for your host platform. Check the table of
+  supported versions above to determine which version of VirtualBox is supported
+  for the Apertis Release you want to use.
 
 - Follow the installation procedure provided in the
   [VirtualBox installation guide](https://www.virtualbox.org/manual/ch02.html)