Make it easier for volunteers to find instructions / check their volunteer time

[misaugstad]

Brief description of problem/feature

We could definitely make it easier for volunteers to find the instructions for submitting hours and to find the page that shows them how much time they've volunteered. Here are my proposed changes:

1. If they marked their account as a service hours volunteer, add link(s) to the instructions and/or time check page to the navbar for them.
2. Add a place on the user dashboard where you can mark your account as a volunteer for service hours or not.

[misaugstad]

@JeremyFreiburger when signing up on Project Sidewalk, there is a checkbox asking whether the user will be submitting volunteer service hours and that is saved in the database. If you check that box, it brings you to the /serviceHoursInstructions page after signing up. And on that page, it says that you can check your hours on the /timeCheck page (with a link). Feel free to test out this flow locally, or on the https://sidewalk-newberg-test.cs.washington.edu/ server. Here's a more thorough list of what I think needs to be done:

1. If the user checked the service hours box, add a link to the /serviceHoursInstructions page in the drop-down menu when clicking on their username (below Your Dashboard). Maybe we call it "Volunteer info" to keep it short.
2. If the user checked the service hours box, also add a link to the /timeCheck page below the "Volunteer info" link in that drop-down. "Time check" is a fine name for it.
3. On the instructions page, let's tell them that this is where they can find that info. Here's what I have written now. After I link to the timeCheck page, just add that they can find both of these pages if they are signed in by clicking on their username in the top-right of the page, and include an example screenshot of what that looks like.
4. Add a checkbox to the admin dashboard to let them mark themselves as a service hours volunteer or not. Probably we don't want to mess with the nice look of the page by sticking it at the top, even though it feels like it fits next to the drop down for choosing an organization. But if you think you can make it look good up there, then by all means!

[misaugstad]

Oops forgot to share the screenshot of what it looks like rn: