feat: create hover view

[KevinWu098]

WIP To-Dos

• [x] Show all meetings of the section
• [x] Handle hovered sections that are already added
• [x] Disable in added pane (possibly solved by task 2)
• [x] Make not an eyesore

Summary

1. Implement a HoveredStore to store the currently hovered course
2. SectionTableBody will access and update HoveredStore when a section is hovered
3. Hovered Courses will be appended to events passed to the Calendar

Test Plan

1. Check that it correctly displays the course on the calendar
2. Light and Dark mode compatibility
3. Doesn't activate on Added Pane
4. Doesn't activate on already added courses

Issues

Closes #828

Future Followup

1. Remove the schedule conflict feature, since this covers much of the same functionality? Unsure on this (since SC is my baby 🥺, but it's a valid question)

[KevinWu098]

TL;DR of latest changes:

1. "Hovered" courses are now 80% opacity
2. Settings Menu has some updated styling
3. Preview Mode is now in settings menu, defaulting false

I've chosen not to move Schedule Conflict into the experimental menu, as after some further thought, I agree with Eric on that it's a feature people have gotten used to, but I'm happy to circle back to that as needed