Documentation: Add supported and tested motherboards to the list

I tested both motherboards and they seem to boot Serenity correctly :)

Documentation/HardwareCompatibility.md

@@ -18,3 +18,5 @@ Serenity boots to a graphical desktop on all machines unless otherwise noted.
 | ---------------------------------------- | ----------------------------- |
 | Intel Desktop Board D915GAG / D915PSY    | Pentium 4 HT CPU              |
 | Intel Desktop Board D875PBZ              | Pentium 4 HT CPU              |
+| Gigabyte G31M-ES2L             | ICH7 2009 machine with IDE controller only |
+| Asus PRIME B360-PLUS      | Has only one PS2 port, AHCI works |