Update generated READMEs to include prerequisites

[npentrel]

We ran into an issue when user testing because the ultrasonic sensor didn't explain a board was needed. This is to fix future issues. See viam-modules/viam-ultrasonic#6 for context.

[michaellee1019]

I like the idea that we need to describe which attributes are viam dependencies vs strings. A few thoughts:

• Where this is won't show up on the machine builder, since the model level docs start with the ## model heading. I think we should move to a ### prerequisites. Otherwise it will only show on the registry detail page.
• After using viam for a while, the copy/paste of attributes is more important and should be "above the fold". Could we put after the JSON snippet? Its hard to balance expert users vs first time user experience. My feeling is that first time users will read the entire markdown. Thoughts?
• Wondering if we should recommend that the type field is dependency instead of string then describe that the attribute is a string of the name of the associated viam resource?