Increase Mentor Availability

[nzeager]

Is your feature request related to a problem? Please describe.
This is a feature request. I would like to encourage and make it easier for more mentors to sign up for more availability. Right now we only have a few mentors signing up intermittently, and it would be good to increase that.

Describe the solution you'd like
We should have some way for mentors to sign up for recurring times, so they don't manually have to add time every 3 days to remain available. The format for this isn't decided, but I think it could make sense to have times able to repeat either once a week on that day, every weekday, or every day.

Describe alternatives you've considered
There are a few other ways we could encourage mentor participation. More suggestions are welcome.
-Automate an email to mentors at the beginning of a day if no one has signed up (this could be toggled on or off).
-Add a note on the scheduling page if no mentors are signed up asking them to request a mentor session in the momentum-mentors-app slack channel.
-Reminders (either from instructors or automated) requesting mentors during certain times that students may have more questions (calculator app, beginning/end of final projects, etc).

[nzeager]

New suggestion: Set up automated email for Sunday to remind mentors to sign up. Maybe randomize wording so it's not always the same?