Add Web Team Deploy window

Following a conversation with Steph, Jon, Tyler, and Nat, we're going to put in place a reserved window for web to do backport deploys and config changes outside the band of the typical backport window, as we've been having issues finding deployers. This is somewhat intended to be temporary, as hopefully the soon forthcoming deploy UI will make this no longer necessary, but for the time being let's enable we deploys!

Note that the time is not consistent across days due to availability on the calendar, and I left a note as discussed informing people that this will be skipped regularly. Please let me know if there's any other information I can provide here to be helpful!!

Preview of new schedule from running the make-deployments-calendar script: https://wikitech.wikimedia.org/wiki/User:Stoyofuku-wmf/deploy_calendar_test

Bug: T381541