Capture line loss

# :rocket:

- [x] Is your feature request essential for your project?

### Describe the workflow you want to enable
I wish I could configure loss of transmission lines (ac & dc) in the optimization formulation. In the current implementation, transmission lines are lossless which sometimes limits our capability of modeling components in practice, especially when trying to come up with equivalent sub-system without inducing new components.

### Describe your proposed implementation, if applicable
We will need to add constraints in `model.jl` by reading `loss0` and `loss1` fields from the branch table (both ac & dc). Note that the current data structure is inherited from MatPower. We could either follow their convention or not.

### Additional context
We are also considering adding a new component called `link` which is supposed to be more general to be capable to capture losses in both transmission and energy conversion. `link` will be useful in hydrogen and CCUS modeling as well.