chore: Add example

Author: franky47

examples/ThruFilterMap/ThruFilterMap.ino

@@ -0,0 +1,52 @@
+#include <MIDI.h>
+
+using Message = midi::Message<midi::DefaultSettings::SysExMaxSize>;
+
+MIDI_CREATE_DEFAULT_INSTANCE();
+
+/**
+ * This example shows how to make MIDI processors.
+ *
+ * The `filter` function defines whether to forward an incoming
+ * MIDI message to the output.
+ *
+ * The `map` function transforms the forwarded message before
+ * it is sent, allowing to change things.
+ *
+ * Here we will transform NoteOn messages into Program Change,
+ * allowing to use a keyboard to change patches on a MIDI device.
+ */
+
+bool filter(const Message& message)
+{
+    if (message.type == midi::NoteOn)
+    {
+        // Only forward NoteOn messages
+        return true;
+    }
+    return false;
+}
+
+Message map(const Message& message)
+{
+    // Make a copy of the message
+    Message output(message);
+    if (message.type == midi::NoteOn)
+    {
+        output.type = midi::ProgramChange;
+        output.data2 = 0; // Not needed in ProgramChange
+    }
+    return output;
+}
+
+void setup()
+{
+    MIDI.begin();
+    MIDI.setThruFilter(filter);
+    MIDI.setThruMap(map);
+}
+
+void loop()
+{
+    MIDI.read();
+}