Allow array of letters for section header

[Thiousi]

Some alphabets include variations of letters which are typically grouped together in an alphabet list. This would be a great feature to add to this plugin for international support.
For example, maybe we could do something like

const myCustomIndex = [
    "a",
    "b",
    "c",
    "ç",
    "d",
    "e",
    "f",
    ["g", "ğ"],
    "h",
    "i",
    ...
]

Thanks!

Originally posted by @Kieran-McIntyre in #6 (comment)

[dhairyasenjaliya]

@Thiousi are you able to update list dynamically?

[Thiousi]

@dhairyasenjaliya Are you talking about updating the CustomIndex? I haven't tried it.

[dhairyasenjaliya]

@Thiousi No the actual data source object

[Thiousi]

@dhairyasenjaliya I haven't had the need for that use case but I don't see a reason why you wouldn't be able to do it.
AlphabetList is using SectionList, which accepts the extraData prop. See here: https://reactnative.dev/docs/sectionlist#extradata
I have not tried it but don't see a reason for it not working.