Create owners file on devfile registry for default PR reviewers

[elsony]

Which area/kind this issue is related to?
/area registry

Issue Description

There are a couple of cases in the past that some devfile changes in the existing stacks or samples cause problems on individual tools. This item sets an owner for each stack and also a tools representative to allow:

1. stack owner to review the changes
2. tools representative to test out the changes
   before devfile changes get merged to prevent tools breakage and the quality of the devfile changes.

[elsony]

Owners file updated