Initial Qiskit-Plugin

1. Change so that install can either use extras:

• [core] with monodromy and transpile_benchy as python dependencies
• [dev] where they are cloned before install.

2. Implement plugin using: https://qiskit.org/documentation/apidoc/transpiler_plugins.html.

Let's you use Mirage more directly:

from qiskit import transpile

mirage_qc = transpile(
    qc,
    optimization_level=3,
    coupling_map=coupling_map,
    basis_gates=["u", "xx_plus_yy", "id"],
    routing_method="mirage",
    layout_method="sabre_layout_v2",
)