Add guidelines for issue triage

[djzager]

konveyor/enhancements#160 talks about enforcing standards for what it means for an issue (and maybe later) a PR to be triaged. However, we don't currently have a document that details these so called standards.

Create an issue_triage.md that explains:

1. Triaged issues will have a triage/accepted, kind/*, priority/* label. If they don't they will be marked with needs-(triage|kind|priority).
2. If an issue is an issue suitable for new contributors, we should label it good first issue.
3. ... maybe more.

This might be a good reference for ideas on what all might be included in the document...but we aren't really trying to mirror Kube. https://www.kubernetes.dev/docs/guide/issue-triage/#triage-related-tools