config option to use upper tiebar, lower tiebar, or neither with affricates

[wjdenny]

The International Phonetic Association accepts three variants of affricates such as /tʃ/ with a tiebar either above or below the pair of characters. The IPA suggests using them to distinguish true affricates from homorganic stop-fricative sequences as necessary (as is the case in languages like Polish). This leaves it more open to individual preference. Even though the single-character ligatures were removed as of 1989, we could include them as an option.

See: /t͡ʃ/ vs. /ʧ/ vs. /tʃ/ (StackExchange Linguistics)

Future versions will allow overriding any X-SAMPA to Unicode mappings, but it would be helpful to have a configuration option for convenience as the tiebar can be difficult to type and work with.

Here's a proposal.

import { createIpaDecoder } from "ipajs";

const ipa = createIpaDecoder({
   affricateTiebars: "over" // "over" | "under" | "ligature" | "none"
});

console.log(ipa('tS')) // t͡ʃ
console.log(ipa('t-S')) // tʃ

[wjdenny]

Alternatively, it could have two different options: one for using tiebars, ligatures, or nothing with affricates, and another for putting tiebars above or below the character.

import { createIpaDecoder } from "ipajs";

const ipa = createIpaDecoder({
   affricates: "tiebar", // "tiebar" | "ligature" | "none"
   tiebars: "over" // "over" | "under"
});

console.log(ipa('tS')) // t͡ʃ
console.log(ipa('t-S')) // tʃ