Add touchscreen interrupt (closes #1)

[DaAwesomeP]

This is a work in progress, as it requires some modifications upstream to trigger the touchscreen interrupt programmatically. It is working though!

Added functions to touchscreen.cpp (and touchscreen.h respectively):

void Touchscreen::trigger_external_interrupt() { this->store_.touched = true; }

void Touchscreen::setup_external_interrupt() {
  this->store_.init = true;
  this->store_.touched = false;
}

Config example:

touchscreen:
  - platform: ft63x6
    id: m5cores3_touch

esp32_m5stack_core_s3:
  interrupt_pin: GPIO21
  touchscreen: m5cores3_touch