Add core contributors (#1226)
Add core contributors (#1226)

* Start adding core contributors

* Add Alex

* Add Ari and Colin

* Add Aki

* Fix last name alphabetical ordering

* Reorder alphabetically by last name

* Fix name

* Add Mitzi

* Add Seth

* Add Robert
arviz-devs/arviz,arviz-devs/arviz,arviz-devs/arviz,arviz-devs/arviz