feat: add autoflash script for automatic device flashing

Introduce `autoflash.sh` to continuously monitor a specified device
port, automatically flash firmware upon device detection, and log
results. This enhances the flashing process by making it more efficient
and less manual.

Yay for two days of continuous preparing and flashing! :D

autoflash.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+
+# Example usage: ./autoflash.sh /dev/ttyACM0 autoflash_ACM0.log
+
+PORT=${1:-/dev/ttyACM0}
+OUTFILE=${2:-autoflash_ACM0.log}
+
+while true; do
+  echo ""
+  echo "# Waiting for new device on ${PORT}…"
+  while [ ! -e "${PORT}" ]; do
+    sleep 0.5
+  done
+  echo "# Found new device!"
+  sleep 1
+
+  echo "" | tee -a ${OUTFILE}
+  echo -n "========== " | tee -a ${OUTFILE}
+  echo -n $(date -Iseconds) | tee -a ${OUTFILE}
+  echo -n " ${PORT}" | tee -a ${OUTFILE}
+  echo " ==========" | tee -a ${OUTFILE}
+
+  pio run --upload-port ${PORT} --target upload 2>&1 | tee -a ${OUTFILE}
+
+  sleep 1
+  echo "# Waiting for device disconnect…"
+  while [ -e "${PORT}" ]; do
+    sleep 0.5
+  done
+done