Add support for button entities (#2824)

esphome/components/button/button.cpp

@@ -0,0 +1,21 @@
+#include "button.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+namespace button {
+
+static const char *const TAG = "button";
+
+Button::Button(const std::string &name) : EntityBase(name) {}
+Button::Button() : Button("") {}
+
+void Button::press() {
+  ESP_LOGD(TAG, "'%s' Pressed.", this->get_name().c_str());
+  this->press_action();
+  this->press_callback_.call();
+}
+void Button::add_on_press_callback(std::function<void()> &&callback) { this->press_callback_.add(std::move(callback)); }
+uint32_t Button::hash_base() { return 1495763804UL; }
+
+}  // namespace button
+}  // namespace esphome