Export single thread only methods for codecs that have multi-threading.

[jamsinclair]

Is your feature request related to a problem? Please describe.

There is a bug in Vite that prevents the compilation of multi-threaded code in the codecs (See #19). This may take a long time to be fixed.

In the interim the codecs can not be easily used in Vite and Nuxt projects without installing a separate package.

Describe the solution you'd like

The multi-threaded codecs, AVIF, JXL and oxipng could include a single-thread module that can be imported and be compatible with Vite and Nuxt Projects.

E.g.

import { optimise } from '@jsquash/oxipng/single-thread';

Describe alternatives you've considered
N/A

[jamsinclair]

May want to prioritise this sooner as there's still no luck with Vite and multi-threaded modules (See last comment in #19)

[ckellet]

In case it's useful to anyone waiting on this — I've implemented it in a fork: ckellet/jSquash.

Each codec with multiple builds now also exposes entry points bound to a single one:

import encode from '@jsquash/avif/encode';        // bundles all three builds
import encode from '@jsquash/avif/encode-simd';   // bundles one

Same API, same options, same init(). encode.js/decode.js keep their runtime dispatch and behaviour, so it's purely additive — the variants are -simd, -mt and -scalar where each exists.

Both routes are built from a shared factory rather than duplicated, so the default and the variants can't drift apart, and verified against the built output rather than assumed:

dist/encode.js       → avif_enc_mt.js  avif_enc_simd.js  avif_enc.js
dist/encode-simd.js  → avif_enc_simd.js

The motivation was the same one in this issue: on Workers the threaded builds can never load without SharedArrayBuffer, but a bundler following the runtime dispatch emits them anyway. For a deployment using AVIF, JXL and WebP that was 19.95 MB of wasm down to 8.41 MB.

Happy to open a PR here if it'd be welcome.