[Excel, Word] (Bindings) Refresh the Bindings Common API Article (#5306)

* Refresh binding article

* Style tweaks

* Add code ticks to header

* Grammar fix

* Add common API note

* Clean up verbage and Excel example

* Apply suggestions from code review

Co-authored-by: Linda Cannon <[email protected]>

* Address PR feedback

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Co-authored-by: Linda Cannon <[email protected]>

Author: AlexJerabek