support handbook calendly update

Why is this change being made?

Fix / extend support documentation for calendly, which we use a lot for customer scheduled calls.

I couldn't understand why my setup wasn't right, but that was because I was running the company-wide setup, and didn't appreciate there was a difference.

current

• plugin info on customer calls workflow support calendly content
• there's a calendly plugin screenshot intended for that page but the link was broken, and it's gorgeous but very hi res and fills low res screens.

proposed

• created calendly page in workflows as the company-wide onboarding task doesn't set up Calendly the way we use it.
• Removed plugin info from customer calls page and linked both references to single-use to separate page.
• Revised zendesk (including calling out unbabel) onboarding
• Added calendly to workflows

todo

• how does the team round-robin get into folks' call list?
• zoom meeting in the invitation that gets generated
• how does integrate with the zap work? my meetings don't appear in the team calendar.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what