v2.1: Final release coinciding with paper publication

Final release coinciding with publication of the associated paper:

M^cNab, F., Schildgen, T.F., Turowski, J.M. and Wickert, A.D., 2025, Influence of network geometry on long-term morphodynamics of alluvial rivers, Earth Surface Dynamics, 13, p. 1,059-1,092, doi:10.5194/esurf-13-1059-2025.

Since v2, the only changes are to the citation information and the inclusion of a "Key Figure."