Develop utility functions to read-in coastal model output data and pass to `compute_func()`

In coastal areas, diffusive wave downstream boundaries will be 1-way coupled to a tidal model. This coupling is necessary for upstream propagation of coastal energy & water into the inland domain (i.e. backwater conditions). A first step towards this capability is simply reading elevation data from tidal model output files. To do this, I suggest we build an additional utility function to read coastal data and store data in either a numpy array or Pandas DataFrame. Once the data are read-in, we can add an additional argument to the compute_func() call, allowing coastal boundary conditions to be accessed by the routing engine. We don't need to do any computing with the coastal boundary data at this time (i.e. inform boundary conditions), rather can focus on data reading and passing.

Recommended starting point - look at formatted coastal output data.

NOAA-OWP / t-route

Develop utility functions to read-in coastal model output data and pass to `compute_func()` #295