Split and add potential more configurations to the context object

[williamhjcho]

We could make the context object as an accumulator of sorts, where it is merged at the initial I18next.t call to the default options, and just pass it along.
There are also more configuration options to the original implementation that weren't included.

First, we would need to split the interpolator configuration as a separate object within the options and then add the others when possible (might take multiple implementations/PRs)