Add link to Selectize options list in API documentation of Selectize()

[rrlapointe]

I did:

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• [ ] Create a minimal working example on JsFiddle or Codepen (or gave a link to a demo on the Selectize docs)
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When reading the documentation at https://selectize.dev/docs/API/selectize for the Selectize($input, settings) function, there is no reference to where I can find a complete list of keys accepted in the settings object. It just describes the settings as "Options to apply for selectized element" and does not say what options exist. Please include a link to the options list in the API documentation.

Steps to reproduce:

1. Navigate to https://selectize.dev/docs/API/selectize
2. Read the documentation of Selectize($input, settings)
3. Be confused about what the accepted options are

Expected result: As a user, I do not expect there to be critical information in the "Get Started" section that is not in the "API Documentation". As a user, I expect the "API Documentation" to be complete and include everything I need to know if I am not looking for tutorials/working examples.

Actual result: I was confused for days until I saw that this list is included in the "Get Started" section (https://selectize.dev/docs/usage), where I did not initially look for it because I did not expect to find critical API documentation there.