ignore .idea everywhere #470

Job	Run time
build-book	3m 57s
build-microbit-chapter (05-led-roulette)	38s
build-f3discovery-chapter (05-led-roulette)	36s
build-microbit-chapter (07-uart)	38s
build-f3discovery-doc	1m 1s
build-microbit-chapter (08-i2c)	34s
build-f3discovery-chapter (06-hello-world)	22s
build-microbit-doc	2m 10s
build-microbit-chapter (09-led-compass)	37s
build-f3discovery-chapter (07-registers)	25s
build-f3discovery-chapter (08-leds-again)	27s
build-microbit-chapter (10-punch-o-meter)	30s
build-f3discovery-chapter (09-clocks-and-timers)	29s
build-f3discovery-chapter (11-usart)	33s
build-f3discovery-chapter (14-i2c)	26s
build-f3discovery-chapter (15-led-compass)	40s
build-f3discovery-chapter (16-punch-o-meter)	23s
	14m 26s

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