Add code comment for IQPE example

OPENQASM 3;

include "qelib1.inc";

// NISQ-mode lowering to conditional (If) statements

// Compile targeting nisq runtime and a capable QPU:

// (1) Qpp simulator (default):

// qcor -qrt nisq -shots 1024 measure_conditional.qasm -print-final-submission 

// (2) Aer simulator (inspect the QObj to see the use of "conditional" to control quantum instructions)

// qcor -qrt nisq -qpu aer -shots 1024 measure_conditional.qasm -print-final-submission 

// (3) Honeywell: see the OpenQASM2 with if statements.

// qcor -qrt nisq -qpu honeywell:HQS-LT-S1-APIVAL -shots 1024 measure_conditional.qasm -print-final-submission 

// Expected to get 4 bits (iteratively) of 1011 (or 1101 LSB) = 11(decimal):

// phi_est = 11/16 (denom = 16 since we have 4 bits)

// => phi = 2pi * 11/16 = 11pi/8 = 2pi - 5pi/8

// i.e. we estimate the -5*pi/8 angle...

qubit q[2];

const bits_precision = 4;

bit c[bits_precision];

    } else {

      for (const auto &name_to_check : IF_STMT_CAPABLE_QPUS) {

        const auto qpu_name = extra_quantum_args["qpu"];

        if (name_to_check.rfind(qpu_name, 0) == 0) {

        if (qpu_name.rfind(name_to_check, 0) == 0) {

          // QPU start with aer, honeywell, etc.

          // (it could have backend name customization after ':')

          enable_qir_apply_ifelse = true;