12.11 Stokes Theorem Update

[nelong]

• [x] Part b of the preview activity isn’t rendering quite right
• [x] Need example of using stokes thm
• [x] Need to not use previous section (link to flux integrals don’t say previous subsection in text)
• [x] Stoke’s Thm is a bit wordy
• [x] Move activities about surfaces and their boundaries to a subsection on that idea
• [x] Move verifying activities up to beneath the theorem
• [x] Add subsection at end with content dependencies and notes to instructor