Add option to make alphabetical sort decorator case-sensitive

[TaylorKrusen]

PR #5 added an example of a decorator for alphabetical sorting. Someone highlighted the importance of case-sensitivity.

Here's a paraphrased example of sorting challenges caused by casing:

Pretend you're looking for the term "API Keys" on an alphabetically sorted list. Which order would you expect?

Case sensitive	Not case-sensitive
AML API keys Accounts Allowlists Application owners Application users Coupons	Accounts Allowlists AML API keys Application owners Application users Coupons

The redocly-cli solved for this using an ignoreCase flag. A similar solution might work well here.