Update documentation to include new placeBlock config action

Problem/Motivation

Once the placeBlock config action is available (e.g. #3448131: New Config Action: Place Block → is merged), the Recipes documentation should be updated to include this config action and describe what elements are required and what can be omitted, what keywords are available and how they work, and so on.

Proposed resolution

Update all relevant documentation.

Remaining tasks

Update the Available config actions documentation.