Add badge to README for integration tests

[bobcatfish]

Integration tests were added as part of #16

Upside: another badge!
Downside: badge doesn't look good at all XD

Looks like we're still hitting kubernetes/test-infra#9628 so if anyone is looking for a break from build-pipeline that would be super helpful to fix XD

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This pull-request has been approved by: bobcatfish

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[nader-ziada]

Do you want to add the badge anyways? Or wait for it to be fixed in test-infra?

[bobcatfish]

Do you want to add the badge anyways? Or wait for it to be fixed in test-infra?

I could go either way - right now I'm leaning toward adding it anyway, since this issue can effect either of the current badges we have already, but if you lean the other way I'm happy to wait for a fix! and/or try to fix it :)

[nader-ziada]

We can add the badge first, then figure out how to make it green
/lgtm