Feature Request: show estimate of remaining time on the build

[cleverca22]

by prefixing key log lines with ~~~ i have gotten the logs to fold nicely, and buildkite clearly says how long each step of the build took

what i would like next, is for buildkite to grab the average run-time for each step over the last few commits, and then render it in this UI, so it says 1m 10s / 2m 13s, giving you a rough idea of how much longer it will take to finish, and similarly handle the total runtime of the entire script

another optional thing you could then do, is to perform the same checks on everything in the queue, and estimate how long it will take for an agent to become available to run the command