Add automation for interacting with Tekton calendar via gitops

[bobcatfish]

We have a shared Tekton calendar at https://github.com/tektoncd/community/blob/master/contact.md#calendar but at the moment only a couple of people can edit it, so when folks want to reschedule meetings (like @hrishin for the observability working group!), they have to find someone with access to the calendar.

What would be really great is if we could have the expected state of the Tekton calendar committed to this repo, and updates to it would be reflected in the Google calendar.

(And even better, it could be implemented with Tekton itself!)

p.s. this was actually @dlorenc 's idea

[tekton-robot]

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/lifecycle stale

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[bobcatfish]

/lifecycle frozen

I still think it's a good idea (and makes maintainers' lives easier), just needs someone to work on it!