[New model] Add Hedges2004

[chrisleaman]

Who is the published the model and in what year?
Hedges and Mase (2004)

Please provide a link, doi or citation to the paper
Hedges, T.S., Mase, H., 2004. Modified Hunt’s Equation Incorporating Wave Setup. Journal of Waterway, Port, Coastal, and Ocean Engineering 130, 109–113. https://doi.org/10.1061/(ASCE)0733-950X(2004)130:3(109)

If possible, please provide the relevant equation references
This needs double checking as the format the equation is given in isn't very convienent:

• Eqn 5b with coefficients from Table 2: R2

Any other details that would be useful?
For example:

• Data derived from rigid bed phyiscal model and sand beach