It takes a ParamType and returns a decorator function that takes a target, propertyKey, and parameterIndex and stores the parameterIndex and type in a metadata array
ParamType - This is the type of parameter we're defining.
A function that takes in a target, propertyKey, and parameterIndex.
It takes a ParamType and returns a decorator function that takes a target, propertyKey, and parameterIndex and stores the parameterIndex and type in a metadata array