[BUG] Handle opaque in parsing qasm2 strings

[TheGupta2012]

Environment

• PyQASM version: 0.0.2
• Python version: 3.11.6
• Operating system: macOS 14.4

What happened?

PyQASM should gracefully parse the opaque identifier -

ValidationError           Traceback (most recent call last)
Cell In[6], line 1
----> 1 mod = pyqasm.load("""
      2 OPENQASM 2.0;
      3 include "qelib1.inc";
      4 qreg q[2];
      5 creg c[2];
      6 opaque custom_gate (a,b,c) p,q,r;""")

File ~/Desktop/qBraid/repos/pyqasm/pyqasm/entrypoint.py:47, in load(program)
     45         program = openqasm3.parse(program)
     46     except openqasm3.parser.QASM3ParsingError as err:
---> 47         raise ValidationError(f"Failed to parse OpenQASM string: {err}") from err
     48 elif not isinstance(program, openqasm3.ast.Program):
     49     raise TypeError("Input quantum program must be of type 'str' or 'openqasm3.ast.Program'.")

ValidationError: Failed to parse OpenQASM string:

Suggestions (Optional)

Handle opaque in the visitor