Reduce .html size by avoiding duplicating image data

[PeterMinin]

Currently the final .html files include all images as inline base64 data. The problem is, profile photos are typically repeated many times within a chat, and the data is duplicated every time. This makes the files unnecessarily large.

Here is an idea of how to reuse the same data using CSS: https://stackoverflow.com/a/55762229/675674. Note that SVG, which is also used there, is avoidable too: see the comment. Other answers provide other CSS solutions and a JS one.