* implement the focusExchange

* Update refocusExchange.ts

* use Map.forEach and remove keys array

* add tests & docs

* Update docs/api/refocus-exchange.md
Co-authored-by: Phil Pluckthun <phil@kitten.sh>

* fix pkg.json

* Update exchanges/refocus/src/refocusExchange.ts
Co-authored-by: Phil Pluckthun <phil@kitten.sh>

* save bytes by using operation rather than a new object

* add docs to api-index page
Co-authored-by: Phil Pluckthun <phil@kitten.sh>