Improve Get started content structure

[morekid]

We guide people through configuring a few primitives in the Get started guides but we don't really take the time to explain them other than briefly in this intro paragraph.

We should allow more space to explain what we're making people configure, eg:

This configures the following Arcjet rules:

• Shield: protect your app from attacks
• Bot proteciotn: prevent bots from accessing your app
• Rate limit: ...,

Then follow up each rule specifically in the What next section, currently we only follow up on Bot protection:

[morekid]

Consider explaining why we don't provide a test for shield, see: #179 (comment)

[Muhammad-Owais-Warsi]

Hey @morekid , is it ok to explain each term as in this blog. Let me know if I misunderstood something. Thanks!