ESP32 reboot/crashfix

[fluffymadness]

First thank you for this project. I noticed that my esp crashed every few seconds. Debugging via serial told me it is watchdog related I think it is regarding this change https://github.com/esphome/esphome/pull/2846

Basically to stop the esp32 from rebooting every few seconds. App.feed_wtdt() has to be applied before every yield command in InverterMonitor.h, so that the watchdog gets fed accordingly, since the loop execution time is quite long

App.feed_wdt();
yield();