added VMware Workstation, VirtualBox, and Thunderbird.

[ItsJoshBrown]

Add New Icon(s)

Icon Details

Icon ID	Icons
thunderbird
vmwareworkstation
virtualbox
signal

Notes

• Thunderbird: is a free and open-source email client from Mozilla, designed to manage multiple email accounts and streamline communication.
• VMware Workstation: is a powerful desktop virtualization software that allows users to run multiple operating systems on a single physical machine.
• VirtualBox: is an open-source virtualization platform that enables users to create and manage virtual machines, supporting various operating systems.
• signal: is a free, open-source, encrypted messaging app that prioritizes privacy.

Closes

closes #257, closes #247, closes #256

Checklist

• [x] Added icon(s) to the appropriate directory
• [x] Updated documentation with the new icon(s)
• [x] Verified the icon(s) display correctly
• [x] If the icon has light and dark, verified the auto switch works correctly
• [x] The Svg does not contain any sort of strokes