esp32/boards: Provide custom deploy_c3.md for ESP32-C3 boards.

This fixes the flash address for installation on ESP32-C3.

ports/esp32/boards/GENERIC_C3/board.json

@@ -1,6 +1,6 @@
 {
     "deploy": [
-        "../deploy.md"
+        "../deploy_c3.md"
     ],
     "docs": "",
     "features": [

ports/esp32/boards/GENERIC_C3_USB/board.json

@@ -1,6 +1,6 @@
 {
     "deploy": [
-        "../deploy.md"
+        "../deploy_c3.md"
     ],
     "docs": "",
     "features": [

ports/esp32/boards/deploy_c3.md

@@ -0,0 +1,14 @@
+Program your board using the esptool.py program, found [here](https://github.com/espressif/esptool).
+
+If you are putting MicroPython on your board for the first time then you should
+first erase the entire flash using:
+
+```bash
+esptool.py --chip esp32c3 --port /dev/ttyUSB0 erase_flash
+```
+
+From then on program the firmware starting at address 0x0:
+
+```bash
+esptool.py --chip esp32c3 --port /dev/ttyUSB0 --baud 460800 write_flash -z 0x0 esp32c3-20220117-v1.18.bin
+```