Replace Element Web's logo with SchildiChat logo on the error page

[luixxiul]

Before	After

I'm not sure what is the best way of changing the string Element with regard to localization, so I let it as it is.

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• I agree to release my changes under this project's license

[SpiritCroc]

Thanks for finding. For logos we generate automated commits, so it's better to not commit manually but rather add something to icon_gen.sh that overwrites the Element icon. If you want, you can PR a change to add this icon to the script, or I can do it too, as you prefer.

For localization of "Element" strings I haven't decided on an approach yet, probably makes sense if I port over correct_strings.sh from old SchildiChat Android.