Make 1.1 Excludelist checks case insensitive

[Miepee]

Describe the bug
When Atomic creates a modpack for a mod that has not custom music, it goes through all of the songs of the mod and compares them against a 1.1 song excludelist (internally called blacklist) to make sure it doesn't include the 1.1 songs into the modpack. However, since the checks are currently case sensitive, Windows mods which have all lowercase song names (i.e. because they have been ported from Linux via Glenn) will cause a modpack where all the 1.1 songs are included

Expected behavior
Windows mods which have all lowercase songs should not cause a modpack where all 1.1 songs are included

Platform

• OS: Linux
• Version: 2.1.0