Add "Teach" link to sidebar

[outofambit]

https://p5js.org/teach exists and i had no idea! let's link to it from the sidebar

cc @yinhwa ❤️

[yinhwa]

thank you @outofambit for mentioning this!🙌🙌 but i wonder if its ok to add a teach menu to the sidebar, cuz when i first planned for this project with @Qianqianye i hoped not to overload the current menu with the teach page😅 so i wished to instead add like <<Learn "& Teach">> to the current "Learn" heading of Learn page (not the menu itself), but it got me some troubles with dealing with the learn.EJS file 😥

[yinhwa]

also, i've been meaning to update /teach page in this PR since there have been some new submissions for sharing teaching materials ! I've been away from finishing up the PR but will try so in next couple weeks :)

[outofambit]

but i wonder if its ok to add a teach menu to the sidebar, cuz when i first planned for this project with @Qianqianye i hoped not to overload the current menu with the teach page

@yinhwa @Qianqianye mentioned this to me and I'm game for revisiting our sidebar and page structure, but for now the page exists and there's no way to get to it. i'd rather have a long sidebar and have your work be findable until we spend more time figuring out the rest! 💖