Update issue note with info on shared responsibility triage process

In a recent iteration related to issues without a clean owner, we created a decentralized process and triage guidelines to help EMs and PMs to share the load of taking action on those types of issues.

One action as part of this iteration is to provide links to the related documentation as part of the note that the automation posts to the issue when it is automatically classified and a group label is assigned.

This MR adds the verbiage and links to the relevant sections of the handbook.