No self-contained version in latest 1.25.0 release

README [states](https://github.com/jlfwong/speedscope#self-contained-directory) that self-contained (built) version of Speedscope can be downloaded from the releases page:

> If you don't have npm or node installed, you can also download a self-contained version from https://github.com/jlfwong/speedscope/releases. After you download the zip file from a release, simply unzip it and open the contained `index.html` in Chrome or Firefox.

This is amazing thing and greatly helps to bundle speedscope with tools that generates flamegraphs.

However, [v1.25.0](https://github.com/jlfwong/speedscope/releases/tag/v1.25.0) (latest speedscope release at the moment) doesn't include ZIP-archive for some reason while [v1.24.0](https://github.com/jlfwong/speedscope/releases/tag/v1.24.0) does.

Can you please fix it and ensure that future releases will include it too? Thanks!

Start with the README's self-contained directory section and compare the assets on the v1.24.0 and v1.25.0 release pages. Trace the release process that produces the ZIP archive, then verify that a future release includes the self-contained archive alongside the documented download instructions.

Written by the indexing model from the issue text.