This runtime PNG icon (the default window and tray icon) was not updated to
remove the white background when we last changed the branding. This copies a 265
px PNG from elsewhere to ensure it matches.
Part of https://github.com/vector-im/riot-web/issues/9897
instead of the actual electron package. With no way to ignore directories.
I'd like to think of this as temporary, until I get to rip apart riot-web
and riot-electron
Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>