Add support for ESP32 DAC (#1071)

* Add support for ESP32 onboard DAC

* Newlines

* Tests

esphome/components/esp32_dac/esp32_dac.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/core/esphal.h"
+#include "esphome/core/automation.h"
+#include "esphome/components/output/float_output.h"
+
+#ifdef ARDUINO_ARCH_ESP32
+
+namespace esphome {
+namespace esp32_dac {
+
+class ESP32DAC : public output::FloatOutput, public Component {
+ public:
+  void set_pin(GPIOPin *pin) { pin_ = pin; }
+
+  /// Initialize pin
+  void setup() override;
+  void dump_config() override;
+  /// HARDWARE setup_priority
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
+
+ protected:
+  void write_state(float state) override;
+
+  GPIOPin *pin_;
+};
+
+}  // namespace esp32_dac
+}  // namespace esphome
+
+#endif