establish_lake_extents: Establish lake extents
In WDNR-Water-Use/CSLSlevels: CSLS Lake Level Analysis

Defines minimum and maxiumum lake elevations based on deepest point of lake, maximum observed level, and desired contour interval.

1	establish_lake_extents(lake, contour_interval = 0.01, min_deepest = 0)

`lake`	name of lake to analyze, e.g., "Long". Must be present in both CSLSlevels::csls_levels and CSLSdata::lake_levels.
`contour_interval`	interval of contours to use when creating relationship, or precision of lake level (m). Defaults to 0.01.
`min_deepest`	minimum value of deepest vegetation classes (m). Defaults to zero so does not account for vegetation classes deeper than the max elevation of lake.