support for serial read/write buffer (#384)

docs/reference/serial/write-buffer.md

@@ -0,0 +1,11 @@
+# Serial Write Buffer
+
+Write a buffer to the [serial](/device/serial) port.
+
+```sig
+serial.writeBuffer(pins.createBuffer(0));
+```
+
+### Parameters
+
+* `buffer` is the buffer to write to the serial port