Add SAM build and cleanup README

- Add 3.5inch HDZero drone (SAM) with Taker G4 AIO, FlyFishRC Flash 1804
- Add Betaflight dump for SAM
- Clean up README with consistent build attributes across all drones
- Add .gitignore and rates.txt

README.md

@@ -33,6 +33,19 @@ freestyle rigs. All flying on ExpressLRS 2.4GHz with a RadioMaster Boxer.
 - **Motor:** HGLRC Specter 1202.5 / 11000KV / 1-2S
 - **Weight:** ~74g (with battery)
 
+## 3.5 inch — `3.5inch-hdzero/`
+
+- **Name:** SAM
+- **Frame:** Volador VX3.5 O3 Freestyle
+- **Prop size:** 3.5 inch
+- **FC:** Taker G4 45A 8Bit AIO (STM32G473 / ICM42688P) — BF: TAKERG4AIO
+- **ESC:** Taker G4 4-in-1 45A (QF32MT / F4A AIO) / 2-6S
+- **Receiver:** Happymodel EP1/EP2 2.4GHz (ISM2G4)
+- **ELRS firmware:** 4.0.0
+- **VTX:** HDZero Race
+- **Motor:** FlyFishRC Flash 1804 / 3500KV / 4S
+- **Weight:**
+
 ## 5 inch — `5inch-walksnail-moonlight/`
 
 - **Name:**