[client] Fix avatar sizing on Chrome & Safari

[BBaoVanC]

Before this change, on Chrome and Safari (but not Firefox), the svg inside .isso-avatar has a size of 0 by 0 pixels. Not sure why it worked on Firefox, but this makes sense because svg's have no native size, and since there was no minimum size specified, it defaulted to 0.

Instead of just setting width to 48px, I set it to 100% and left max-width set to 48px. It should be better practice this way.

I am wondering if setting height is a good idea, since it seems to have no effect. I kept it in just because it's clearer.

Before (demo on Chromium)

After

[ix5]

As for tests, I have tried getting my hands dirty with puppeteer-based screenshots and comparisons to snapshot png files via imagemagick compare.
E.g. compare -metric AE -fuzz 5% -highlight-color White -lowlight-color Black isso-thread-prev.png isso-thread-new.png x: or simply by comparing image signatures without metadata via identify -quiet -format "%#" {image1,image2}.png

[ghost]

I'm experiencing this issue on firefox/chrome on Linux with the latest isso running on Docker.