Update docs and examples to use ref instead of name for bindings

[savitaashture]

Changes

1. Updated examples and docs to use ref instead of name for bindings
2. Updated signature value in GH README because CEL filters are added as part of this PR Add cel filter for pull request actions in github example #637 which resulted signature validation failure.

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes tests (if functionality changed/added)
• Includes docs (if user facing)
• Commit messages follow commit message best practices

See the contribution guide for more details.

[dibyom]

Thanks @savitaashture
/approve
/lgtm
/kind documentation

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dibyom

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [dibyom]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment