Create shortcode to handle time zones

[rocco8773]

Create a shortcode so we can defined a meeting in a given timezone (e.g. EST) hand have the other timezones (PST and UTC) automatically generated.

It might be possible to store meeting times in web/data/vars.json so the variables are available to all pages/posts. This would allows us to only update vars.json if we change a weekly meeting time, and the change would propagate to all pages/posts.

It would nice to this pinned with a cron job that has the website built, say, at 5am EST every Sunday so time changes from daylight savings is automatically adjusted for.