[DOCS-4729] README updates for Embedded Messaging (#412)

* First round of edits

* More updates to the README

* Extensive updates

* Further updates

* minor fixes

* Added some placeholders

* Some minor updateS

* Removing icon

* Responding to Mitch's feedback

* Update README.md

Co-authored-by: Paul Jung <[email protected]>

* Minor fix as suggested by paul

* Typo

---------

Co-authored-by: Paul Jung <[email protected]>