Added greeting screen on boot

ESP32-ExposureAPI-Scanner.ino

@@ -95,6 +95,13 @@ void setup() {
   // Initialize display
   Serial.println("Init Display");
   display.init();
+  display.clear();
+  display.setTextAlignment(TEXT_ALIGN_CENTER);
+  display.setFont(ArialMT_Plain_24);
+  display.drawString(64, 10, "COVID-19");
+  display.setFont(ArialMT_Plain_10);
+  display.drawString(64, 32, "Exposure API Scanner");
+  display.display();
 
   // Initialize scanner.
   BLEDevice::init("ESP");