Priority Splitter 12-Belt

For each of the 12 input belts, the contents are passed straight through unless the output is backed up; in which case the contents are redirected to an overflow output on the side (could be connected to a trash platform). This happens for each belt separately. Based on the blueprint in this comment: https://steamcommunity.com/app/2162800/discussions/0/6929437446239078173/#c6929437446239201873 . Footprint: 1x1 platform. Input: left, 12 belts. Output: right (primary), 12 belts. bottom (overflow), 12 belts.