feat: congress schedule API

[ryparker]

It would be amazing to have an API that provides the following schedule data:

• Official (house/senate) calendar dates
• Start and predicted end times
• Scheduled recesses
• Cancelled dates
• Added sessions (not on official calendar)
• When a floor session is completed, provide the actual start and end timestamps, and duration
• Which floor sessions are pro forma
• Which dates are district work periods
• Location
• Agenda description
• Agenda references (e.g. ids for legislation, amendments, nominations that are expected to be brought up)

Data for the current congress would be most useful for my use case, however preferably we'd be able to pull this for past congresses as well.