v0.18.1

This release contains a couple bug fixes.

• Avoid newlines between 2 tspan elements by @wouterj in #114. This fixes the annoying horizontal mis-alignment when the tap legend had 3+lines.
• Add an additional u alias for key width in json-format qmk_keyboard. This is sometimes emitted by https://nickcoutsos.github.io/keymap-layout-tools after importing e.g. Kicad PCB files.