Add language alias for Haitian Creole

[BLKSerene]

Description

This PR adds the language alias for Haitian Creole (ht/hat), whose support was added in #13807.

Also replace lists with sets to optimize membership testing.

Types of change

Enhancement

Checklist

• [x] I confirm that I have the right to submit this contribution under the project's MIT license.
• [x] I ran the tests, and all new and existing tests passed.
• [x] My changes don't require a change to the documentation, or if they do, I've added all required information.