feat: Add tachometer sketch

tach/tach.ino

@@ -0,0 +1,35 @@
+// Board: Adafruit Feather M0
+
+#include <Arduino.h>
+
+#include <Adafruit_GFX.h>
+#include "Adafruit_LEDBackpack.h"  // "Adafruit LED Backpack Library" v1.5.0
+
+Adafruit_7segment matrix = Adafruit_7segment();
+
+
+void show(int num) {
+	matrix.print(num, DEC);
+	matrix.writeDisplay();
+}
+
+void setup() {
+	matrix.begin(0x70);
+
+	Serial.begin(115200);
+	// Serial.setDebugOutput(true);
+
+	delay(1000);
+
+	Serial.println();
+	Serial.println();
+	Serial.println("================");
+	Serial.println("BOOT UP");
+
+	show(99999);
+
+}
+
+void loop() {
+;
+}