Sortable column title prop should be localizable

[fo-fo]

A sortable column header has the title Toggle SortBy, which seems to be hardcoded in https://github.com/tannerlinsley/react-table/blob/master/src/plugin-hooks/useSortBy.js#L51. The string should be configurable instead, so that the text can be localized to the user's language.

I'd almost consider this a bug. Maybe there are other strings in need of localization, too?

[fo-fo]

I just realized I can override the prop after applying the header props, but it was still a little bit surprising to find that default title in there. I wouldn't have noticed it without the DOM inspector.