Add new Pico logo

See https://github.com/picocms/Pico/issues/499 and https://github.com/picocms/Pico/issues/499#issuecomment-544136977

img/pico.svg

+<svg height="400" preserveAspectRatio="none" viewBox="0 0 400 400" width="400" xmlns="http://www.w3.org/2000/svg"><path d="m298.4 194.7q0-14.15-.8-31.2l-.85-14.25h-51.05v89.95l8 1.1q9.6 1.05 17.6 1.05 7.95 0 17.5-1.05 4.8-.55 7.95-1.1 1.65-22.2 1.65-44.5m-69.75-45.8h-49.3v182.45l7.7.85q9.3.8 17 .8 12.3 0 24.6-1.65z" fill="#2eae9b" transform="translate(-38.85 -40.95)"/></svg>
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