Add legislative calendar feature

Great idea - definitely a future build [Matt]

This page lists some key deadline that drive the entire legislative session -

https://malegislature.gov/ClerksOffice/House/Deadlines

Note that these deadlines shift each session (and sometimes there are ad hoc extensions).

@mvictor55 and I discussed today that it would be a nice-to-have to integrate this in the website for users' informational purposes.

Here's a proposal about how to do it:

* At the start of each session, manually generate a Google Calendar with the key deadlines
* At an embedded widget on the homepage displaying that Google Calendar
* Provide some user education about how they can import the calendar to their personal calendars