Need advice on tech stack for web based chat aggregator

I don't know where else to ask for advice on this. So, excuse me, if it's not the right place.

I'm thinking of creating a hobby project. It's a web based chat aggregator with plugin system so that 3rd party developers can integrate more chat apps.

I specifically chose this one because I have no idea how to start making it. What tech stack should I use? What kind of architecture should I choose?