Improve 209 in Chrome with OffiDocs

DESCRIPTION

Some changes to the csc209 (2023 winter) website coordinated by Professor Rosenbloom

quality of life changes for the CSC209 winter 2023 website

Features
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* dark mode based on system colour scheme
* C syntax highlighting based on highlight.js
* popup to quickly access lecture slides

Links
* current link is now bolded in the navbar
* external links now open in a new tab
+ new tab links have an indicator
* main nav better complies with fitts law (bigger click targets)
* fixed the broken piazza link
* added a link to submit labs and stuff in the main nav

Lecture Notes
* reordered lecture notes so they're reverse-chronological (newest is at the top)

Improve 209 web extension integrated with the OffiDocs Chromium online