Add timezone conversion capability to table documenting available hosts

[kbeyls]

https://llvm.org/docs/GettingInvolved.html#office-hours documents available hosts for office hours. It documents the time of the session in 1 time zone, as picked by the host. It would be helpful if there was a straightforward way to be able to convert the timezone to a preferred timezone for the person potentially dialing in.
Would a link to a time zone conversion service be a simple solution for this?

[llvmbot]

@llvm/issue-subscribers-infrastructure