Documents new selector API

[ahrjarrett]

This PR adds documentation to support the addition of the new selector API for TypeScript users.

The approach I took was simply to add tabs anywhere API usage differed between JavaScript and TypeScript:

Here's the companion PR for i18next-gitbook

Checklist

• only relevant code is changed (make a diff before you submit the PR)
• [-] run tests npm run test
• [-] tests are included
• commit message and code follows the Developer's Certification of Origin

Checklist (for documentation change)

• only relevant documentation part is changed (make a diff before you submit the PR)
• motivation/reason is provided
• commit message and code follows the Developer's Certification of Origin