fix(img): restore icon256.png lost during webp migration (73d6ed0)

[KhaledSaeed18]

fix: restore src/img/icon256.png to resolve broken README logo

Summary

Restores src/img/icon256.png, which was lost during the icon format migration and not recovered in the subsequent cross-browser icon support commit, causing the README logo to render as a broken image.

Root Cause

Commit	Description	Effect on icon256
e3e9b82	Convert PNG images to WEBP	icon256.png replaced by icon256.webp
73d6ed0	Cross-browser icon support (SVG on Gecko, PNG on Chromium)	icon256.webp removed, icon256.png not re-added

The README has referenced src/img/icon256.png throughout both commits. After 73d6ed0 landed, no file exists at that path.

Changes

• src/img/icon256.png — restored from commit c053486 (last commit prior to the WEBP migration)

Verification

README logo renders correctly with this file in place. No other references to icon256 in the codebase are affected.

Closes #544

[hackademix]

Thank you very much for your contribution.
Rather than re-adding the png file, though, I'd prefer src/img/logo-full.svg (already there) to be used in README.md.
Can you amend this patch? Otherwise I'll do it myself.

Thanks!

[KhaledSaeed18]

Hello @hackademix
Done, removed src/img/icon256.png, switched to src/img/logo-full.svg, and added an alt attribute.

[hackademix]

lgtm!

Merging, thank you!