Translations to review

This issue is a reminder to keep track of some incomplete translations to review in the future.
e.g. for links pointing to english content and for which doesn't yet exist an italian version.

- [ ] [shiftIn.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Advanced%20IO/shiftIn.adoc) - In the description there is a link to the english version of the SPI library reference
- [ ] [shiftOut.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Advanced%20IO/shiftOut.adoc) - In the description there is a link to the english version of the SPI library reference
- [ ] [shiftOut.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Advanced%20IO/shiftOut.adoc) - On the top of the example there is a link to the english version of an official arduino tutorial
- [ ] [tone.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Advanced%20IO/tone.adoc) - Links on the bottom of the document refer to english tutorials
- [ ] [analogRead.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Analog%20IO/analogRead.adoc) - A link on the bottom of the document refer to an english tutorial
- [ ] [analogReference.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Analog%20IO/analogReference.adoc) - A link on the bottom of the document refer to an english tutorial
- [ ] [analogWrite.adoc](https://github.com/arduino/reference-it/blob/master/Language/Functions/Analog%20IO/analogWrite.adoc) - Some links in the document refer to english tutorials

Review the listed .adoc files under Language/Functions/Advanced IO and Analog IO, starting with shiftIn.adoc and shiftOut.adoc. Check each referenced English SPI or Arduino tutorial link and determine whether an Italian version exists. Done means the listed incomplete translation links have been reviewed and the checklist items are resolved.

Written by the indexing model from the issue text.