Note: Webdev, like all skills, is a thing that you learn by doing. So whether it's through club projects or your own projects, learning webdev is a must if you want to build things. In practice, this will consume >90% of the effort you spend when building applications. Don't spend all of your time watching videos and reading articles, and instead build simple stuff like tic-tac-toe or todo-lists
An overview of HTTP - HTTP is a thing every web developer needs to understand, at least at a high level, and this MDN article gives a pretty-good overview of it.
Understanding the DOM - The Document-Object-Model, or "DOM" for short, is the interface a web-browser uses for representing a webpage and allowing JavaScript to read and modify its content and/or structure. This blog series from DigitalOcean explains it pretty well.
JavaScript/TypeScript - Javascript pretty much runs the world at this point. It's ecosystem is to gargantuan that pretty much any user-facing application you can build with something other than Javascript can be build much faster with Javascript, considering many things you'd typically end up having to implement yourself is just an npm install away. That said, the language is quite messy and things very quickly get out of hand as a project grows. Thus, being familiar with its quirks and common ways to deal with them is really important. In fact, this topic is so large that it gets its own page.
Fireship's youtube channel is a gold mine for all things webdev - their videos are very short, helpful, and sometimes funny. It's a great thing to subscribe to and keep an eye on for cool stuff.
Here are some of their playlists and/or videos I highly reccomend: