Treeshaking

Tree shaking could be a problem if we are talking about interpolating between the libraries! But here is a question of how we can populate the code as a couple of tree-shakable functions and still make it replaceable?

Refs: https://github.com/gpbl/react-day-picker/issues/980

Start with the issue discussion and the referenced react-day-picker issue 980; no files, tests, or entry points are identified here. The work is done only after the project agrees on how tree-shakable functions can remain replaceable and documents or implements that design.

Written by the indexing model from the issue text.