Add guidance on scheduling meetings for team members in US timezones

Why is this change being made?

As a follow on to Sid's update to his communication preferences, the Global Voices TMRG thought this is a great opportunity to add clarifying guidelines to address the scheduling friction that global team members have shared. The are a couple of key benefits to our organization from this MR:

1. The organization will become more efficient as there should be more options to schedule cross-regional meetings with global team members. Thus, resulting in less time to schedule meetings, faster time to collaboration..
2. The workplace environment of global team members may improve from a reduction of calls scheduled outside of working hours, reducing the sense of burnout and helping team members prioritize friends-and-family

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

---