Error when downloading file with whitespace in Url

[ViRb3]

Hello,

I discovered a bug where InstanceSync would fail to download a file with a whitespace in its downloadUrl. Example:

"downloadUrl": "https://edge.forgecdn.net/files/2691/750/AbyssalCraft Heads-1.12.2-2.1.0.jar"

I implemented a fix here, but it may not be the best approach.

P.S. If you want to adopt the changes from my fork let me know and I will gladly assist you.