Add a TROUBLESHOOTING doc with WiFi password notes (mjg59#563)

* Add a TROUBLESHOOTING doc with WiFi password notes

* Update TROUBLESHOOTING.md

Co-authored-by: Felipe Martins Diel <41558831+felipediel@users.noreply.github.com>

TROUBLESHOOTING.md

@@ -0,0 +1,9 @@
+# Troubleshooting
+
+## Firmware issues
+
+### AP setup fails with non-alphanumeric passwords
+
+Some devices ship with firmware that cannot connect to WLANs with non-alphanumeric passwords. To fix this, update the firmware to the latest version. You can also change the password to one with just letters and numbers or create a separate guest network with a simpler password.
+
+_First seen on Broadlink RM4 pro 0x6026. Already fixed in firmware v52079._