Does anyone here have any experience writing a browser extension/plug-in? I have a fairly simple idea that I think would work well for a plug-in, but have zero knowledge about creating one.

I want a plug-in that will scan the page (probably through the source code) for any youtube links, and automatically add them all to a new youtube playlist, which could either be an actual saved playlist or to your watch later list if you're signed in. How difficult would this be for someone who knows how to create browser extensions?