[workflows] Add initial OWNERS and Readme

[dibyom]

Changes

Add initial OWNERS file and Readme for workflows

ref: tektoncd/community#464

Submitter Checklist

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

• Includes docs (if user facing)
• Commit messages follow commit message best practices
• Commit messages includes a project tag in the subject - e.g. [OCI], [hub], [results], [task-loops]

See the contribution guide
for more details.

[dibyom]

/assign @bobcatfish
/assign @vdemeester

[bobcatfish]

/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bobcatfish, vdemeester

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 [bobcatfish,vdemeester]

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

[bobcatfish]

let's doooo it 🥳

/lgtm