Feat/mfa ts samples (aws-amplify#5624)

* Initial commit

* chore:address PR feedback

* chore:add mfa ts and js examples (#3)

Co-authored-by: idevk <idevk@amazon.com>

* Revert "chore:add mfa ts and js examples (#3)"

This reverts commit ef0305f.

* chore:add mfa samples

* Apply suggestions from code review

Batch commit of all initial review changes

Co-authored-by: israx <70438514+israx@users.noreply.github.com>

* Apply suggestions from code review

line replacement test

* Apply suggestions from code review

add try/catch for TS and JS blocks

* Apply suggestions from code review

update location of Auth.currentAuthenticatedUser() call

* Apply suggestions from code review

Final changes

---------

Co-authored-by: idevk <idevk@amazon.com>
Co-authored-by: Chris Womack <67726635+cwomack@users.noreply.github.com>
Co-authored-by: israx <70438514+israx@users.noreply.github.com>