all_time_stats expects `dist_XXXX` columns in year ascending order

[jessjaco]

Perhaps just a note in the docs is needed, but all_time_stats expects any columns to be ordered by ascending year in this section:

dea-coastlines/coastlines/vector.py

Lines 1162 to 1168 in 155ef96

	# Select date columns only
	year_cols = x.index.str.contains(col)
	subset = x.loc[year_cols].astype(float)
	# Restrict to requested initial year
	subset.index = subset.index.str.lstrip("dist_").astype(int)
	subset = subset.loc[initial_year:]

Particularly this line:

subset = subset.loc[initial_year:] 

(I also see a hardcoded "dist_" string that should be replaced by col)