Addition of controlled rotation gates

Would it be possible to add support for controlled rotation gates (`CRx(gate)`, `CRy(gate)`, `CRz(gate)`) in the `braket.circuits.gate` module?

``` python
class CRx(Gate):
r"""Controlled Rx gate.

Unitary matrix:

.. math:: \mathtt{CRx} = \begin{bmatrix}
1 & 0 & 0 & 0 \\
0 & 1 & 0 & 0 \\
0 & 0 & \cos{(\phi/2)} & -i \sin{(\phi/2)} \\
0 & 0 & -i \sin{(\phi/2)} & \cos{(\phi/2)} \\
\end{bmatrix}.
"""
```

Thank you!