Add more Tekton injection sources

[fproulx-boostsecurity]

https://pipelinesascode.com/docs/guide/authoringprs/#advanced-event-matching

event_title
body
files
body.issue.title
body.issue.body
body.pull_request.body
body.pull_request.comment
body.pull_request.head.ref
body.pull_request.head.repo.default_branch
body.pull_request.head.label