samd/boards: Add default deploy instructions.

Signed-off-by: robert-hh <robert@hammelrath.com>

ports/samd/boards/deploy.md

@@ -0,0 +1,10 @@
+For deploying the MicroPython firmware to the SAMD module, follow
+the procedure:
+
+-  Push the reset button twice or call machine.bootloader(). A drive
+   icon should appear representing a virtual drive.
+
+-  Copy the .uf2 file with the required firmware to that drive.
+
+As soon as the drive disappears, the firmware is loaded and started.
+