Make the index default case insensitive

[Jogai]

Sorry, maybe a bit out of the blue, but I think files named "Index" (note the uppercase) should work as a default too.

[posva]

Hello! Any reason to support this? Usually, a project has linting rules to avoid inconsistent case naming, so in this case, I would say it's better to only support lower case index for the convention and let people use a linter to detect this kind of issue.

[Jogai]

Well, all my files and folders are pascal case, so I use Index instead of index