Add board renders and the carrier STEP model to the V2 READMEs

PCB/v2.x/snips/README.md

@@ -7,6 +7,13 @@ Stackup library plus a [local thumbstick model](stackup/parts.kdl). The existing
 through `snips_controller.stackup_sch`; sync it with the Stackup KiCad plugin. Run
 `stackup check PCB/v2.x/snips/stackup/board.kdl` from the repository root before syncing.
 
+<p align="center">
+  <img src="assets/snips-v2-front.png" alt="KiCad render of the front of the Snips V2 board, with the thumbstick, macro buttons, ESP32 module and USB-C port" width="300">
+  <img src="assets/snips-v2-back.png" alt="KiCad render of the back of the Snips V2 board, with the power circuits, the carrier pads and the battery connector" width="289">
+</p>
+
+A STEP model of the assembled board is in [`step/v2.0/snips_controller.step`](step/v2.0/snips_controller.step).
+
 ## V2 board
 
 70 x 30 mm, 4 layers: F.Cu signals, In1 solid 3V3, In2 solid GND, B.Cu signals. 1.6 mm thick. Routed, not yet fabricated.

PCB/v2.x/xbee-carrier/README.md

@@ -2,6 +2,13 @@
 
 A 2-layer castellated daughter board that puts a Digi XBee 3 PRO Micro on the V2 controller's underside. It is optional, and V2 runs without it. The mating footprint on V2 is `U_XBEE1`, `XBee_Carrier_Castellated`.
 
+<p align="center">
+  <img src="assets/xbee-carrier-v1-front.png" alt="KiCad render of the XBee side of the carrier, with the XBee 3 Micro, its U.FL connector and the support parts around the edge" width="400">
+  <img src="assets/xbee-carrier-v1-back.png" alt="KiCad render of the mating side of the carrier, with the castellated edges and the label This side faces V2" width="368">
+</p>
+
+A STEP model of the assembled board is in [`step/xbee_carrier.step`](step/xbee_carrier.step).
+
 ## Board
 
 - **Size:** 22 x 17 mm, 0.8 mm thick, 2 layers. The chamfer clears the MH3 shell post on V2.