Optimize simplification of polys

[lindsayplatt]

Currently using rmapshaper::ms_simplify(0.5) but this number could be much lower to increase the polygon simplification. Would be interesting to explore this affect on the overall size of the final SVG. Probably should parameterize this in some way.

[cnell-usgs]

Similarly, we should look at file sizes with different levels of rounding in the sf_to_coords function. It's currently at 6, but I expect we might only need 2-3 digits to keep the same look, but reduce the file size.