Add words to hyphenated words list

[vr8hub]

A few more words run across either in reviews or in my current production, all in M-W.

While adding mantelshelf, I noticed we have both mantelpiece(s) and mantlepiece(s). M-W says (scroll down to the Did You Know?) that mantel and mantle aren't really synonyms, although the latter is sometimes used, "especially in American English," for the former. Ngrams reflects that; mantlepiece is barely above zero, mantelpiece is a couple of order of magnitudes more common. (In English fiction; it's even more pronounced in English in general.)

So, I wonder if we should change mantle-?piece to mantelpiece in spelling.py, and remove mantlepiece(s) from words? There are 45 occurrences of mantlepiece in the corpus that would need to be changed.
Ditto for mantle-?shelf; we have four of those in the corpus, vs. 117 of mantelshelf.

cotehardie(s)
mantelshelf
mantelshelves
tumbledown

[acabal]

Sure, I think we can do that if you can open a PR for the toolset.