Add demo in the README.md

[Fei-Guo]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind documentation

What this PR does / why we need it:

This PR adds the live dome for openyurt + edgex integration in the README.md

[rambohe-ch]

/lgtm
/approve

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Fei-Guo, rambohe-ch

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[rambohe-ch]

/lgtm