Switch images to svgs, where possible (#1563)

Closes #1361, #1362

assets/img/svg/3rd-party/etherpad.svg

@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="128" height="128" version="1.1" viewBox="0 0 33.867 33.867" xmlns="http://www.w3.org/2000/svg"><g transform="translate(0 -263.13)"><g transform="matrix(.072143 0 0 .072143 -44.234 303.31)" stroke-linecap="round" stroke-linejoin="round"><g fill="none" stroke-width="14.66"><path d="m848.76-422.01 18.457 182.66m110.24 75.286-110.62-75.286-144.71 68.86" stroke="#0e300b"/><path d="m847.97-424.39-129.76 254.9 127.11 74.631 2.51-379.49-0.38271 49.19 130.01 261.09-132.13 67.706m-39.053-234.63 43.208 24.929 43.738-26.908m-129.01 79.91 85.275 50.969 86.416-46.192" stroke="#185014"/><path d="m781.41-483.32c9.5596-80.144 115.64-95.56 133.9-2.1599" stroke="#185014"/></g><ellipse cx="847.58" cy="-480.02" rx="8.7388" ry="8.9519" fill="#b3b3b3" stroke="#185014" stroke-width="19.547"/></g></g></svg>