Add option to treat tool names as case-insensitive

[SamButNotSam]

This issue builds onto #41

Was trying to install wally earlier, followed the guide and aftman was saying it's not in my aftman.toml when it is. After I changed the name from "wally" (lowercase w) to "Wally" (uppercase W, the same name as in the aftman bin) it worked fine. Why is this the case when the official wally docs use it in lowercase?