Updated articles for Arduino Cloud & Provisioning 2.0 [HC-1672, HC-1673, HC-1675, HC-1687]

[seaxwi]

Four new/updated Help Center articles for Provisioning 2.0:

• Add a device to Arduino Cloud. This article previously documented a three-step process of (1) adding a device, (2) creating a Thing and (3) uploading the Thing sketch. The updated article is dedicated only to adding new devices, splitting (2) to a new article (see below).
• Associate a Thing to a device. New article.
• If your device is offline in Arduino Cloud. Note that this article is distinct from If your device can't be added to Arduino Cloud.
• Configure the network credentials for a device

[colandre]

LGTM