Add informational hints to operator documentation covering behaviors
that may differ from user expectations, particularly for those
familiar with jq:
- slice-array: clarify that slicing only works on arrays, not strings
- select: document behavior when piping select to a literal value
- equals: note bash history expansion with != operator
- create-collect-into-object: mention that shorthand {key} syntax
is not supported
- collect-into-array: explain difference between [.x | .[]] and [.x[]]