UnrealScript language support

[angelbruni]

UnrealScript is a scripting language used on Unreal Engine before UE4 was a thing. I currently use it on Unreal Development Kit, which is basically a free version of UE3. There's also modders who use it to mod games such as older Unreal Tournament games.

This is my first ever pull request and I've also never made a VSCode extension, so if I did something wrong while adding the language support, I would like to know where I got it wrong. Thank you.