sch: add bottloader info

passkey.kicad_sch

@@ -2914,6 +2914,17 @@
 		)
 		(uuid "4ddeb7f5-a37c-42bc-8bf1-2345ea4cc68c")
 	)
+	(text "DFU bootloader\nwill still boot\nwhen flash empty"
+		(exclude_from_sim no)
+		(at 179.832 66.548 0)
+		(effects
+			(font
+				(size 1.27 1.27)
+			)
+			(justify left)
+		)
+		(uuid "519d643b-4380-4fdd-8c08-6526f8388cb5")
+	)
 	(text "MCU has built-in\n1.5k D+ pull-up"
 		(exclude_from_sim no)
 		(at 28.575 35.56 0)