I have been interested in the idea of computer clusting which is about making multiple pysical computer system to act as one whole logical computer system computing the same task at the same time, but what about this idea in the quantum computing world has it been done or proposed before?
Yes, this has been thought about. For example, the plan for scaling up ion trap computers involves having multiple "modules", each with a few dozen qubits. When qubits in separate modules need to interact, they are moved to the same module using quantum teleportation or some other quantum channel. Each "module" is like a little quantum computer in a cluster, with the cluster forming a larger quantum computer.