Add Qiskit code assistant prompts

[javabster]

Goal: 10 pages across our docs site that includes the new code assistant prompt admonition. Prompts should be relevant to the content of the page where the admonition is added.

Example copy:

Not sure what gate you're looking for? Ask the Qiskit code assistant:

    # Add a Y-gate to qubit 4, controlled by qubits 0-3

Haven't installed the Qiskit Code Assistant extension yet? install here[link].