ws2812: update examples to use go:build tags required by go 1.17

Signed-off-by: deadprogram <ron@hybridgroup.com>

examples/ws2812/arduino.go

@@ -1,3 +1,4 @@
+//go:build arduino
 // +build arduino
 
 package main

examples/ws2812/digispark.go

@@ -1,3 +1,4 @@
+//go:build digispark
 // +build digispark
 
 package main

examples/ws2812/others.go

@@ -1,3 +1,4 @@
+//go:build !digispark && !arduino && !qtpy
 // +build !digispark,!arduino,!qtpy
 
 package main

examples/ws2812/qtpy.go

@@ -1,3 +1,4 @@
+//go:build qtpy
 // +build qtpy
 
 package main