added serial demo and fixed some issues with str

Examples/Arduboy-Tutorials/serial/src/lib.rs

@@ -0,0 +1,44 @@
+#![no_std]
+#![allow(non_upper_case_globals)]
+
+//Include the Arduboy Library
+#[allow(unused_imports)]
+use arduboy_rust::prelude::*;
+
+#[allow(dead_code)]
+const arduboy: Arduboy2 = Arduboy2::new();
+
+// Progmem data
+
+// dynamic ram variables
+
+// The setup() function runs once when you turn your Arduboy on
+#[no_mangle]
+pub unsafe extern "C" fn setup() {
+    // put your setup code here, to run once:
+    arduboy.begin();
+    arduboy.set_frame_rate(30);
+    arduboy.clear();
+    serial::begin(9600)
+}
+
+// The loop() function repeats forever after setup() is done
+#[no_mangle]
+#[export_name = "loop"]
+pub unsafe extern "C" fn loop_() {
+    // put your main code here, to run repeatedly:
+    if !arduboy.next_frame() {
+        return;
+    }
+    if serial::available() > 0 {
+        let intcoming_byte = serial::read_as_utf8_str();
+        serial::print("I received: \0");
+
+        serial::println(intcoming_byte);
+    }
+    if arduboy.pressed(A) {
+        serial::println("kekw")
+    }
+
+    arduboy.display();
+}