feat: Add Arduino fixture file for language recognition test

tests/fixtures/languages/arduino/test.ino

@@ -0,0 +1,21 @@
+// Simple Arduino sketch
+
+void setup() {
+  // Initialize serial communication
+  Serial.begin(9600);
+  pinMode(LED_BUILTIN, OUTPUT);
+}
+
+void loop() {
+  // Main code that runs repeatedly
+  digitalWrite(LED_BUILTIN, HIGH);
+  delay(1000);
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+  Serial.println("Blinking LED");
+}
+
+// A custom function
+int calculateDelay(int baseDelay, int multiplier) {
+  return baseDelay * multiplier;
+}