Add LED matrix scrolling text sketch

sketches/led_matrix_scrolling_text/README.md

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+# LED Matrix Scrolling Text
+
+Løbetekst til den indbyggede 12×8 LED-matrix på Arduino UNO R4 WiFi.
+
+Teksten ruller fra højre mod venstre og gentages efter en kort pause:
+
+> Kan AI skrive programmer til Arduino? Tjek https://iot.p20.dev
+
+Sketchen bruger de officielle biblioteker `ArduinoGraphics` og
+`Arduino_LED_Matrix`. `ArduinoGraphics` kan installeres med:
+
+```powershell
+arduino-cli lib install ArduinoGraphics
+```
+
+## Kompilering
+
+```powershell
+arduino-cli compile --fqbn arduino:renesas_uno:unor4wifi sketches/led_matrix_scrolling_text
+```
+
+## Upload
+
+Upload først efter godkendelse:
+
+```powershell
+arduino-cli upload --port COM5 --fqbn arduino:renesas_uno:unor4wifi sketches/led_matrix_scrolling_text
+```
+

sketches/led_matrix_scrolling_text/led_matrix_scrolling_text.ino

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+#include <ArduinoGraphics.h>
+#include <Arduino_LED_Matrix.h>
+
+// Scrolling text demo for the Arduino UNO R4 WiFi 12x8 LED matrix.
+
+constexpr unsigned long SCROLL_SPEED_MS = 75;
+constexpr unsigned long REPEAT_PAUSE_MS = 1000;
+
+const char MESSAGE[] =
+  "Kan AI skrive programmer til Arduino? Tjek https://iot.p20.dev";
+
+ArduinoLEDMatrix matrix;
+
+void setup() {
+  matrix.begin();
+  matrix.textFont(Font_5x7);
+  matrix.textScrollSpeed(SCROLL_SPEED_MS);
+  matrix.clear();
+}
+
+void loop() {
+  matrix.beginDraw();
+  matrix.stroke(0xFFFFFFFF);
+  matrix.beginText(12, 1, 0xFFFFFF);
+  matrix.print(MESSAGE);
+  matrix.endText(SCROLL_LEFT);
+  matrix.endDraw();
+
+  matrix.clear();
+  delay(REPEAT_PAUSE_MS);
+}
+