Feedback on new rust documentation logo background

[ekuber]

@kornel

Solid outline can be faked with 4 or 8 sharp shadows offset by 1 pixel.

    filter: drop-shadow(1px 0 0px #fff)
        drop-shadow(0 1px 0 #fff)
        drop-shadow(-1px 0 0 #fff)
        drop-shadow(0 -1px 0 #fff);

looks like this: