[DOCUMENTATION] Add VM testing guide

[youngcoder45]

Create a guide to test the distro in a virtual machine.

Context:
README recommends VM testing but doesn’t explain how.

Suggested approach:

1. Create docs/VM-TESTING.md
2. Include:
   • VirtualBox setup
   • QEMU setup
   • ISO usage

Acceptance criteria:

• Clear step-by-step VM guide

Files:

• docs/