Reworked Power Supply, New Instrumentation Amp, Fixed Bad Math

The global IC shortage has necessitated a redesign on a couple fronts. The power supply on the previous release was still giving us trouble, and it recently went out of stock so it seemed like a good opportunity to re-examine what we needed from it and try something new. Now it is a -3V line, using a voltage pump followed by an LDO.

The second major change was for the primary amp, the INA333. It is now out of stock, so we used a pin-for-pin replacement: the INA818. It also has a gain of 10000 V/V, hopefully an upgrade over our previous limit of 1000 V/V.

Lastly, we're still testing designs for our silkscreen to create something that's fun but also reflects our commitment to open source hardware.