standardize sigil delimiters

[novaugust]

With a sigil like ~w, a codebase might use a variety of delimiters, for no reason other than the author's personal preferences.
Styler could enforce a standard for delimiters, ala our string delimiter choices.

For example:

defp style({:sigil_w, [{:delimiter, _} | meta], children}), do: {:sigil_w, [{:delimiter, "("} | meta], children}

This naive approach would break code like this though: ~w|)|, so the sigil should be evaluated for which delimiter would require the fewest escapes, and otherwise use the delimiters by preference