* Change _delay_ms/us() to wait_ms/us()
* Switch to platform-agnostic GPIO macros
* Add AVR spi_master and migrate Adafruit BLE code
* Set verbose back to false
* Add clock divisor, bit order and SPI mode configuration for init
* Add start and stop functions
* Move configuration of mode, endianness and speed to `spi_start()`
* Some breaks here would be good
* Default Adafruit BLE clock divisor to 4 (2MHz on the Feather 32U4)
* Remove mode and divisor enums
* Add some docs
* No hr at EOF
* Add links in sidebar
* Update japanese translation of newbs.md and related documents.
* document link id change
* add `ja/` in each link
`[xxx](yyy.md)` --> `[xxx](ja/yyy.md)`
* copy docs/ja/_summary.md from umi-umi's #7248 and fix it